STEM OnLine Mini Dictionary

An essential mini-dictionary for STEM minds. A list of selected terms from science, technology, engineering, and mathematics, with clear, straightforward, and engaging definitions right at your fingertips.

Ablation

The total loss of ice and snow from a glacier due to melting, evaporation, or the calving of icebergs.

Abscissa Axis

The horizontal line in the Cartesian plane, generally represented by the variable $x$.

Absolute Frequency

The number of times a specific value or response occurs within a data set.

Absolute Value

The numerical magnitude of a value regardless of its sign, defined as the positive distance between that number and the origin.

Absolute Zero

Theoretical minimum temperature (0 K or -273.15 °C) at which particles reach their minimum energy level.

Absorbed Power

Total power consumed by a receiver or component to perform its function and cover its internal losses.

Acceleration

Change in the velocity vector of a body per unit of time as a result of a net force.

Acid

Substance that has a pH lower than 7 and is capable of releasing hydrogen ions in a solution.

Acid Salt

Salt containing replaceable hydrogen atoms in its structure, coming from a partially neutralized polyprotic acid.

Activation Energy

Minimum amount of energy required for a chemical reaction to start. It is usually measured in joules per mole (J/mol).

Active Elements

Circuit components capable of supplying electrical energy or controlling current flow, such as power supplies.

Additive Synthesis

Method of obtaining colors by adding lights of different wavelengths, used in screens and RGB systems.

Air Resistance

Friction force exerted by the atmosphere that opposes the motion of a falling body.

Albedo

Proportion of sunlight that a planetary surface reflects back into space.

Algebra

Branch studying structures and operations using symbols and formal rules.

Algebraic Equality

An expression including numbers and letters (variables), which can be true for certain values or for all of them.

Alkane

Hydrocarbon composed only of carbon and hydrogen atoms joined by single bonds.

Alkyl Group

Structure resulting from removing a hydrogen atom from an alkane, allowing it to attach to a main chain as a branch.

Alpha Emission (α)

Type of decay where the nucleus emits a heavy particle composed of two protons and two neutrons (Helium-4 nucleus).

Alternating Current

Type of electric current in which charges periodically change direction.

Altitude

Vertical distance of a point relative to sea level (m); it is the main factor determining pressure variation.

Ammeter

Instrument designed to measure current intensity; it must always be connected in series within the circuit.

Amphoterism

Chemical ability of water to act as an acid or a base depending on the substance it reacts with.

Amplitude

Maximum displacement value of an oscillating body relative to its equilibrium position.

Analemma

Figure-eight curve representing the Sun’s position if observed daily at the same time.

Analytical Chemistry

Branch of chemistry studying methods to identify and quantify chemical substances.

Anemometer

Instrument used to measure wind speed.

Angle

The opening formed by two rays with a common origin called a vertex; its standard SI unit is the radian (rad), though it is commonly measured in degrees (°).

Angle of Incidence

Angle formed between the incident ray and the normal line at the point of contact with the surface.

Angle of Refraction

Angle between the normal line and the light ray propagating through the second medium.

Angular Displacement

Angle swept by an object in circular motion, generally measured in radians.

Angular Frequency

Measure of the rotation rate or the rate of change of the motion’s phase, expressed in radians per second (rad/s).

Angular Velocity

Rate at which an object’s angular displacement changes per unit of time.

Anion

Ion with a negative electrical charge formed when a neutral atom gains one or more electrons.

Antecedent

The first term of a ratio (numerator) that is compared with the second to establish a quantitative relationship.

Anticyclonic Wind

Air rotating outward from a high-pressure center.

Calculus

Branch of mathematics analyzing change using derivatives, integrals, and limits to solve continuous problems.

Calorie

Amount of energy required to raise the temperature of one gram of pure water by 1 °C. It is equivalent to 4.184 J.

Capacitance

Ability of a component to store electric charge per unit of potential difference, defined as C = Q / V and measured in Farads (F) in the SI.

Capacitor

Passive component designed to store electrical energy in the form of an electrostatic field between two conductive plates.

Capacitor Charging

Dynamic process in which a capacitor accumulates energy, its voltage increasing exponentially until it equals that of the source.

Capacitor Discharging

Dynamic process in which a capacitor releases stored energy through a resistor, its voltage decreasing exponentially to zero.

Carbon Dioxide

Main greenhouse gas generated by burning fossil fuels and respiration.

Cartesian Plane

A two-dimensional system formed by two perpendicular graduated lines that allow any point to be located using a pair of coordinates $(x, y)$.

Catalyst

Substance that increases the rate of a chemical reaction without being consumed or permanently altered in the process.

Catalytic Electrode

Conductive surface that facilitates the redox reaction of external gases without being consumed or degraded during the process.

Cathetus

Each of the two sides that form the right angle in a right triangle.

Cation

Ion with a positive electrical charge formed when a neutral atom loses one or more electrons.

Celestial Equator

Great circle on the celestial sphere resulting from projecting Earth’s equator into space.

Celestial Meridian

Great circle passing through the celestial poles and an observer’s zenith.

Celestial Pole

Intersection points of Earth’s rotation axis with the celestial sphere.

Celestial Sphere

Imaginary sphere of infinite radius, centered on the Earth, onto which celestial bodies are projected.

Center of Buoyancy

Point where the buoyant force is considered to be applied, coinciding with the center of gravity of the displaced fluid volume.

Center of Gravity

Specific point where the resultant gravitational force of a body is considered to act.

Center of Mass

Geometric point where the entire mass of a system is considered concentrated for motion analysis.

Centrifugal Force

Apparent force that tends to move a body away from the center of rotation when observed from an accelerated system.

Centripetal Acceleration

Quantity that measures the change in velocity direction of a body following a curved path.

Centripetal Force

Net force directed toward the center of the trajectory that forces a body to follow a curve.

Chain Reaction

Fission process where released neutrons strike other heavy nuclei, causing a series of successive and self-sustained fissions.

Change in Momentum

Change experienced in a body’s momentum, which is numerically equal to the received impulse.

Charles’s Law

States that, at constant pressure, the volume of a gas is directly proportional to its absolute temperature (V₁/T₁ = V₂/T₂).

Chemical Bond

Set of forces that hold atoms, ions, or molecules together to form more complex and stable structures.

Chemical Compound

Substance formed by the chemical union of two or more elements in defined proportions.

Chemical Element

Pure substance formed by atoms with the same number of protons.

Chemical Energy

Potential energy stored in chemical bonds that is released or absorbed during a reaction.

Chemical Equation

Symbolic representation of a chemical reaction showing the substances that react and those that are produced.

Chemical Law

General relationship experimentally verified that describes the behavior of chemical substances.

Chemical Model

Simplified representation of chemical substances or processes allowing study and prediction.

Chemical Property

Characteristic of a substance describing its behavior during a chemical transformation.

Chemical Quantity

Measurable property of a chemical system expressed using a numerical value and a unit.

Chemical Reaction

Thermodynamic process in which one or more substances transform their molecular structure and bonds to form new substances.

Chromatic Aberration

Optical defect common in refractors where colors do not focus at the same point, creating colored edges.

Dalton’s Law

States that the total pressure of a gas mixture is equal to the sum of the partial pressures of each individual gas.

Damping

Energy dissipation process in an oscillatory system that gradually reduces the amplitude of motion.

Data Distribution

The way the values of a variable are organized and spread, allowing for the identification of patterns and trends.

Declination

Celestial coordinate equivalent to latitude, measured north or south of the celestial equator.

Decomposition Potential

Minimum external voltage that must be applied to an electrolytic cell for electrolysis to occur continuously.

Decomposition Reaction

Process in which a single compound fragments into two or more simpler substances.

Definition

Precise explanation of the meaning of a concept within a formal system.

Deformation

Change in the length or shape of an elastic body (stretching or compression) relative to its equilibrium position.

Degree

Angular measurement unit that divides a circle into 360 equal parts (°).

Degree Celsius

Temperature unit based on the freezing (0 °C) and boiling (100 °C) points of water at standard pressure.

Degree Fahrenheit

Temperature scale where the freezing point of water is 32 °F and the boiling point is 212 °F.

Denominator

The lower number that determines how many equal parts the unit is divided into; it can never be zero due to mathematical impossibility.

Density

Scalar quantity expressing the amount of mass per unit volume of a substance, measured in kg/m³ in the SI.

Dependent Variable

A magnitude whose value is determined by the function’s correspondence rule when applied to the independent variable.

Derivative

A function that measures the rate of change of one variable with respect to another, mathematically representing the slope of the curve at each point.

Destructive Interference

Phenomenon that occurs when waves meet in phase opposition, subtracting their amplitudes and potentially canceling each other out.

Deuterium

Stable isotope of hydrogen containing one proton and one neutron in its nucleus.

Dew Point

Specific temperature to which an air mass must be cooled to reach saturation and begin condensation.

Diagonal

A line segment connecting two non-consecutive vertices of a polygon.

Diatomic Gas

Molecule formed by two atoms of the same element, as occurs with elemental hydrogen in nature.

Dielectric

Insulating material that, when placed between the plates of a capacitor, increases its capacitance by reducing the internal electric field.

Dielectric Strength

Maximum electric field intensity that an insulator can withstand before becoming conductive (breakdown).

Differentiability

A property of a function that guarantees the existence of its derivative at a given point or interval.

Diffuse Reflection

Scattering of light in multiple directions when striking a rough surface, preventing the formation of sharp images.

Diffusion

Process by which the particles of one gas gradually mix with those of another due to their random thermal motion.

Digital Circuit

Electrical circuit operating with discrete signals represented by defined levels.

Dilution

Procedure that consists of decreasing the concentration of a solute by adding more solvent.

Diminished Image

Type of image produced by diverging lenses that is always smaller in size than the actual object.

Direct Current

Type of electric current in which charges move always in the same direction.

Direct Proportion

A relationship where an increase in one magnitude causes a proportional increase in the other, keeping their quotient constant.

Direct Proportionality

Relationship in a voltage divider where a higher resistance corresponds to a higher voltage drop (V ∝ R).

Direction

The straight line upon which the vector lies, defined by the angle it forms with the reference axes.

Displaced Volume

Space occupied by the fluid that has been moved aside by the body upon immersion, measured in m³ in the SI.

Displacement

Vector quantity that measures the change in position of an object from its initial point to its final point.

Dissipated Power

Part of the electrical power that is lost in the form of heat due to the resistance of components or conductors.

Dissipative Force

Force that transforms work into non-recoverable energy, usually heat (such as friction), depending on the path.

Exothermic Reaction

Chemical reaction that releases energy into the environment, generally in the form of heat or light.

Expansibility

Tendency of gases to occupy the entire volume of their container due to the null attraction force between their particles.

Experiment

Controlled process allowing the study of physical phenomena and verification of theories.

Explosion

Interaction where internal energy is transformed into kinetic energy, separating the components of a system.

Exponential Curve

Non-linear mathematical graph describing the rate at which voltage or current varies, being rapid at first and slowing down at the end.

External Angle

An angle formed by one side of a polygon and the extension of the adjacent side.

Extrapolation

Inference of values outside the observed data interval, assuming that the model’s behavior remains constant.

Extremes and Means

Elements of a proportion where the product of the extremes must equal the product of the means to be valid.

Eyepiece

Lens or system of lenses located near the focus that magnifies the image formed by the objective.

Faraday’s Law

Law stating that the induced electromotive force (EMF) is proportional to the rate of change of magnetic flux: ε = -dΦ / dt.

Ferromagnetic Core

Material (such as iron) placed inside a coil to concentrate field lines and multiply its inductance.

Ferromagnetism

Property of materials like iron that exhibit strong magnetization in the presence of an external magnetic field.

Field Lines

Visual representation of the direction and strength of the electric field; they originate from positive charges and terminate at negative charges.

Final Velocity

Velocity vector possessed by a body at the instant the study interval of its motion is concluded.

Fissionable Isotope

Variety of a chemical element (such as Uranium-235) whose nucleus is capable of undergoing fission after capturing a neutron.

Fixed Pulley

Device with a stationary axle that changes the direction of the force without changing its magnitude.

Flight Time

Total duration an object remains in the air from the start of a jump until it returns to the reference level.

Flow

Continuous movement of a mass of fluid through a space or conduit in a specific direction.

Flow Rate

Volume of fluid passing through a section per unit of time (Q = V / t), measured in m³/s in the SI.

Fluid Mechanics

Branch of physics studying the behavior of liquids and gases in motion.

Focal Length

Path that light travels from the objective to the point where the sharp image is formed.

Focal Point (Focus)

Point where parallel reflected rays converge in a concave mirror (or from which they appear to originate in a convex one).

Focus

One of the two interior fixed points that define the shape of an orbital ellipse.

Focusing

Adjustment of the distance between the lens and the image plane so that the rays converge exactly on a detector surface.

Foehn Wind

Dry and warm wind descending the leeward slope of a mountain.

Force

Interaction capable of modifying the state of rest or motion of a body, or of producing a deformation in it.

Foucault Pendulum

Long-length device used to demonstrate Earth’s rotation through the precession of its oscillation plane.

Fourier Coefficients

Numerical values that determine the amplitude or weight of each sine and cosine in the reconstruction of the original function.

Fourier Series

The representation of a periodic function as an infinite sum of sinusoidal functions (sines and cosines) with different frequencies.

Fourier Synthesis

The process of reconstructing a complex signal by superimposing its individual sinusoidal components.

Fraction

An expression representing the division of a quantity into equal parts, indicating how many of those parts are taken from the total.

Frame of Reference

Set of conventions used by an observer to measure the position and motion of a body.

Free Fall

Particular case of uniformly accelerated motion where the acceleration is gravity and there is no air resistance.

Frequency

Number of complete turns or revolutions an object makes in a given unit of time.

Frequency Domain

Analysis of a function through its spectral components, showing how much energy exists at each frequency.

Friction

Force that opposes the relative motion between two surfaces in contact.

Friction Force

Force opposing motion that arises from the interaction between two surfaces in contact.

Fuel Cell

Type of galvanic cell designed to operate continuously by the external flow of reactants toward the electrodes.

Fulcrum

Physical place on which an object pivots or rests to transmit or multiply a force.

Function

Relation assigning to each element of a set exactly one element of another set.

Fundamental Frequency

The lowest frequency in a Fourier series that defines the basic period of the original function.

Galaxy

Huge collection of stars, gas, and dust bound by gravity.

Galvanic Cell

Electrochemical device that transforms chemical energy into electrical energy through spontaneous electron transfer reactions.

Gamma Radiation (γ)

Emission of high-frequency electromagnetic waves with high penetrating power that often accompanies alpha and beta processes.

Gas

State of aggregation of matter in which particles have minimum attraction to each other and occupy the entire volume of the container.

Half-life

Time required for half of the nuclei in a radioactive sample to decay into a different element.

Harmonics

Sinusoidal components of the series whose frequencies are integer multiples of the fundamental frequency.

Heat

Thermal energy in transit from one body to another. It is measured in Joules (J), though the calorie (cal) is used, where 1 cal = 4.184 J.

Height

The perpendicular distance measured from the base to the furthest point or vertex of a figure.

Heliocentric Model

Astronomical theory that places the Sun at the center of the system and the planets revolving around it.

High Tide

The moment when sea water reaches its maximum height within the tidal cycle; it is measured in meters (m) or feet (ft) relative to the mean level.

Hohmann Transfer Orbit

Orbital maneuver that uses two engine pulses to move a spacecraft between two circular orbits.

Homologous Series

Group of organic compounds with the same chemical function that differ only by the number of methylene groups.

Hooke’s Law

Physical principle stating that the force exerted by a spring is proportional to its deformation, measured in joules (J) regarding work performed.

Horizontal Displacement

Change in position of an object measured exclusively along the axis parallel to the horizon.

Hydration

Ability of some salts to incorporate water molecules into their crystal structure in a constant manner.

Hydraulic Press

Device that multiplies a force through the area ratio F1 / A1 = F2 / A2, based on Pascal’s principle.

Hydride

Chemical compound formed by the combination of hydrogen with any other element, whether metallic or non-metallic.

Hydrogen

Chemical element with atomic number 1, the lightest in the periodic table, which under normal conditions occurs as a diatomic gas (H₂).

Hydrogen Bond

Especially strong dipole-dipole interaction between the hydrogen atom of one water molecule and the oxygen of another.

Hydrostatic Pressure

Pressure due to the weight of a fluid at rest, calculated as P = ρ · g · h and measured in Pascals (Pa) in the SI.

Hygrometer

Precision instrument designed to measure the moisture content in the atmosphere.

Hyperopia

Visual defect where images are focused behind the retina; it is corrected through the use of convex lenses.

Hypocenter

Point inside the Earth where the rupture that generates the seism originates; its depth is measured in kilometers (km).

Hypotenuse

The longest side in a right triangle, opposite the right angle.

Ice Sheet

A mass of glacial ice covering more than 50,000 km² of land and flowing in all directions (e.g., Antarctica and Greenland).

Ideal Gas

Theoretical gas composed of point particles with random displacements that do not interact with each other, following the gas laws.

Ideal Gas Law

Equation of state relating pressure, volume, temperature, and moles of a gas through the expression PV = nRT.

Image of a Point

The specific value returned by the function when evaluated at a concrete value within its domain.

Impact Force

Intense force acting over a very short period of time, characteristic of collisions and crashes.

Impedance

Total opposition a circuit offers to the flow of alternating current; it combines resistance and reactances, measured in Ohms (Ω).

Improper Fraction

A fraction whose numerator is equal to or greater than the denominator, indicating the value is equal to or greater than one whole.

Impulse

Vector quantity product of the applied force by the time interval of action, measured in N·s.

Impulse-Momentum Theorem

Physical relationship stating that the impulse applied to a body equals the change in its linear momentum.

Incident Ray

Light beam that propagates toward a reflective surface before interacting with it.

Inclination

Degree of deviation of a surface or line from the horizontal or vertical.

Inclined Plane

Flat surface forming an angle with the horizontal plane, used to raise or lower bodies with less effort.

Incompressible Fluid

Substance whose density is assumed constant (ρ = constant in the SI) under pressure changes, such as most liquids.

Increment (Δx)

The difference or variation between two values of the independent variable used to calculate the rate of change.

Independence of Motions

Principle that allows decomposing a complex motion into simultaneous simple motions that do not interfere with each other.

Independent Event

An event whose probability of occurrence is not affected by the previous outcome of another distinct event.

Magnetic Declination

Angle between true north and the north indicated by a compass.

Magnetic Dipole

System composed of two opposite poles (north and south); isolated magnetic poles (monopoles) do not exist in nature.

Magnetic Energy

Energy accumulated within the magnetic field generated by the inductor during the passage of electric current.

Magnetic Field

Region of space where a moving electric charge experiences a magnetic force, measured in Teslas (T) in the SI.

Magnetic Flux

Measure of the amount of magnetism passing through a surface, calculated as Φ = B · A · cos(θ) and measured in Webers (Wb) in the SI.

Magnetic Permeability

Ability of a material to allow magnetic field lines to pass through it, measured in H/m in the SI.

Magnetic Pole

Point on the Earth’s surface where the magnetic field lines are vertical.

Magnetic Reversal

Event in which the Earth’s magnetic north and south poles swap positions.

Magnetosphere

Region around the Earth dominated by its magnetic field that deflects solar wind.

Magnification

Ratio between the size of the formed image and the actual size of the object observed through the lens.

Magnifying Glass

Optical instrument consisting of a short-focal-length convex lens that produces a virtual, upright, and enlarged image.

Magnitude

Any physical or mathematical property that can be measured or counted and expressed through a numerical value.

Mantle

Intermediate layer of the Earth located between the crust and the core.

Mars

Fourth planet, called the Red Planet due to the iron oxide on its surface.

Mass

Amount of matter in a body, constant throughout the universe. The SI unit of measurement is the kilogram (kg) and in the English system the pound (lb).

Mass Number

Sum of the number of protons and neutrons present in the nucleus of an atom, represented by the letter A.

Mass-Energy Equivalence

Physical principle stating that the energy released in a nuclear reaction comes from a small loss of mass during the process.

Materials Chemistry

Branch of chemistry studying structure, properties, and applications of solid and functional materials.

Mathematical Equality

A proposition of equivalence between two expressions separated by the = sign, indicating they both represent the same logical value.

Mathematical Function

A dependency relationship between two magnitudes where each input value corresponds to exactly one output value.

Mathematical Ratio

A binary link between two magnitudes expressed as a quotient to determine how many times one contains the other.

Maximum Kinetic Energy

Excess energy possessed by the electron after being released, which depends solely on the frequency of the incident light.

Measurement Resolution

The smallest variation in the measured quantity that the instrument is capable of detecting and displaying on its screen.

Measuring Instrument

Device used to measure electrical quantities within a circuit.

Mechanical Advantage

Numerical ratio indicating how much the applied force is multiplied in a simple machine relative to the resistance.

Mechanical Energy

Sum of the kinetic energy and potential energy of a body or system in a given state.

Mechanical Wave

Type of wave that strictly requires a material medium (solid, liquid, or gas) in order to propagate.

Mechanical Work

Scalar quantity resulting from force by displacement and the cosine of the angle between them, measured in joules (J).

Median

The central value of an ordered data set that divides the sample into two equal parts, with 50% of the data above and 50% below.

Melting point

Temperature at which a substance changes from solid to liquid state at a given pressure.

Member

Each of the two expressions located on either side of the equal sign; called the first and second members.

Membrane Electrolyte

Selective barrier that allows the passage of specific ions between electrodes while blocking the direct passage of electrons and gases.

Mercalli Scale

Qualitative scale that measures seismic intensity based on observed effects and damage to people and structures.

Mesh (Loop)

Any closed path in a circuit that does not contain other closed paths within it.

Mesh Equation

Mathematical expression resulting from applying the voltage law to a closed path to find unknown currents.

Mesosphere

Middle layer of the atmosphere where temperature reaches its lowest levels and most meteoroids disintegrate.

Product

Substance formed as a result of a chemical reaction, written to the right of the arrow in the equation.

Projectile Motion

Two-dimensional motion whose curved trajectory results from the combination of a uniform horizontal advance and a vertical free fall.

Proof

Logical reasoning establishing the truth of a theorem or mathematical proposition.

Propagation Speed

Speed at which the perturbation travels, defined by the product of frequency and wavelength.

Proper Fraction

A type of fraction where the numerator is smaller than the denominator, always representing a value less than one whole unit.

Proportion

A statement of equality between two ratios, ensuring that the relationship between magnitudes remains constant on both sides.

Proportionality Constant

A fixed value relating two magnitudes; obtained by dividing any pair of corresponding values in a relationship.

Protection Elements

Components designed to interrupt the circuit in case of overload or short circuit to prevent damage (fuses, circuit breakers).

Proton

Subatomic particle with a positive electrical charge of 1.602 × 10⁻¹⁹ C located in the atom’s nucleus.

Pulley

Simple machine consisting of a grooved wheel that rotates on an axle, used to move bodies; the work performed is measured in joules (J).

Quadrant

Each of the four regions into which the axes divide the Cartesian plane, numbered I to IV in a counterclockwise direction.

Quantization

Phenomenon by which physical quantities such as energy cannot vary continuously, but in discrete steps or packets”.”

Quantum Algorithm

Sequence of logical operations executed on a quantum computer to perform specific tasks with superior efficiency.

Quantum Computing

Computing paradigm that leverages phenomena such as superposition and entanglement to solve problems unreachable for classical computers.

Quantum Cryptography

Secure communication method that uses the laws of quantum physics to detect any attempt at data interception.

Quantum Decoherence

Process by which a quantum system loses its superposition properties due to interaction with the environment, becoming classical”.”

Quantum Entanglement

Intimate connection between particles where the state of one instantaneously depends on the state of the other, regardless of the distance separating them.

Quantum Mechanics

Branch of physics describing the behavior of matter and energy at atomic scales, where the laws of classical physics are no longer valid.

Quantum Probability

Measure of the possibility of a system being in a certain state after a measurement is performed, replacing classical certainty.

Quantum State

Physical condition describing all measurable properties of a system at the subatomic level at a given moment.

Quantum Supremacy

Point at which a quantum computing device can perform a calculation that is practically impossible for the most powerful classical supercomputer.

Quantum Teleportation

Process of transferring quantum state information to a remote location using entanglement and classical communication.

Qubit (Quantum Bit)

Basic unit of quantum information that, thanks to superposition, can represent 0, 1, or both states simultaneously.

Radial Velocity

Component of an object’s velocity that moves directly away from or toward the observer.

Radian

Angle measurement unit in the SI representing the central angle whose arc length is equal to the radius; it is approximately equal to 57.29°.

Radiant Energy

Energy transmitted through electromagnetic waves that can propagate through a vacuum.

Radiative Forcing

Change in the atmosphere’s net energy flow caused by climate factors.

Radio Telescope

Specialized antenna that captures radio waves from astronomical sources in space.

Radioactivity

Spontaneous process of decay of unstable atomic nuclei through the emission of particles and electromagnetic energy.

Radius of Curvatura

Design parameter defining the shape of the lens surface and determining its ability to converge or diverge light.

Radius of Rotation

Constant distance between the center of the circular path and the position of the moving particle.

Random Experiment

A process or action whose exact outcome cannot be predicted with certainty before it occurs, even under the same initial conditions.

Range or Image

The subset of values in the codomain that are actually reached by the function when the full domain is applied.

RC Circuit

Electrical configuration consisting of a resistor and a capacitor that exhibits time-dependent dynamic behavior.

Reactance

Opposition to the flow of alternating current due to inductance or capacitance, causing a phase shift between voltage and intensity.

Reactant

Initial substance that participates in a chemical reaction and is consumed to form new products.

Real Focal Point

Point where light rays physically converge after passing through a convex lens, allowing images to be projected.

Real Gas

Gas that does not behave exactly according to ideal laws due to intermolecular interactions and the actual volume of its particles.

Real Image

Image formed by the actual convergence of reflected rays, which can be projected onto a surface.

Real Numbers

The set comprising all rational and irrational numbers, allowing for the infinite continuity of the number line.

Reciprocal

The result of transposing the terms of a fraction; multiplying it by the original fraction always results in the number one.

Redshift

Phenomenon where an object’s light shifts toward longer wavelengths because it is moving away from the observer.

Reflected Ray

Light beam that moves away from the surface after bouncing off the point of incidence.

Reflecting Telescope

Instrument that uses curved mirrors instead of lenses to collect and focus light.

Reflexive Property

An axiom stating that every quantity is equal to itself (a = a), a fundamental basis of identity.

Refracted Ray

Light beam that, after passing through the separation surface between two media, continues its propagation in a different direction.

Salt

Chemical compound formed by cations and anions through an ionic bond, typical result of the reaction between an acid and a base.

Salt Hydrolysis

Reaction of the ions of a dissolved salt with water, which can alter the pH of the solution.

Sample

A representative subset selected from a population upon which statistical observations and measurements are performed.

Sample Space

The set of all possible outcomes that can result from a given random experiment.

Satellite

Body orbiting a planet, natural or artificial.

Saturated Air

State in which the air contains the maximum possible amount of water vapor for a given temperature (100% relative humidity).

Saturated Hydrocarbon

Organic compound containing the maximum possible number of hydrogen atoms per carbon, with no double or triple bonds.

Saturation

State of a solution containing the maximum amount of solute that the solvent can hold at a given temperature.

Saturn

Gas giant famous for its extensive and bright ring system.

Scale

A constant proportion of measurement that establishes the unit distance between numbers, ensuring a coherent graphic representation.

Scatter Plot

A two-dimensional graphical representation of data where each point represents the value of two variables, allowing visual identification of their correlation.

Sea Breeze

Local wind blowing from the sea toward the land during the day.

Secant Line

A line that intersects a curve at two points; its slope represents the average rate of change between those two values.

Seism

A synonym for earthquake, commonly used in technical contexts to refer to any vibratory movement of the earth.

Seismic Wave

Elastic wave that propagates the energy of an earthquake; its propagation speed is measured in kilometers per second (km/s).

Seismograph

Precision instrument used to detect, measure, and record Earth’s vibrations.

Self-Induction

Phenomenon by which a changing current in a coil induces an electromotive force within itself to oppose the change in flux.

Semi-major Axis

Half of the longest diameter of an ellipse, used to define the size of an orbit.

Semiconductor

Material whose ability to conduct electricity is intermediate and can be controlled under certain conditions.

Sense

The orientation of the vector’s arrow, indicating towards which end of the direction it is headed.

Series Circuit

Configuration where components are connected one after another, so that the same current flows through all of them.

Series Inductors

Configuration where coils are connected one after another, directly adding their values to obtain a higher equivalent inductance.

Series Measurement

Connection method of an instrument (such as an ammeter) where the current must mandatorily pass through the equipment.

Short Circuit

Path of virtually zero resistance joining two points of different potential, causing a dangerous increase in current.

Short-Circuit Current

Maximum current delivered by the original circuit when its two output terminals are directly connected to each other with zero resistance.

Simple Harmonic Motion

Periodic back-and-forth motion in which a body oscillates about an equilibrium position under the action of a restoring force.

Simple Pendulum

Idealized model consisting of a point mass suspended from an inextensible, weightless string.

Simplification

The technique of reducing a fraction to its lowest terms by dividing both the numerator and denominator by a common divisor.

Sine

Trigonometric ratio defined as the quotient between the side opposite an angle and the hypotenuse.

Sinusoidal Waves

Smooth mathematical functions describing repetitive oscillations, fundamental for signal analysis.

Sliding

Relative motion between two surfaces in contact without rolling.

Slope

A measure of the inclination of a line relative to the horizontal axis, calculated as the ratio of vertical change to horizontal change.

Slope of the Curve

A numerical value indicating the steepness of the tangent line to the function at a specific point in the domain.

Snell’s Law

Principle relating the refractive indices of two media to the angles of incidence and refraction of light.

Solar Corona

Outermost layer of the Sun’s atmosphere, made of plasma and visible during total eclipses.

Solar Declination

Angle between the Sun’s rays and the plane of the Earth’s equator.

Vector Component

Projection of a vector quantity onto the axes of a coordinate system to analyze its effects independently.

Vector Components

Projections of a vector onto the axes of the Cartesian coordinate system.

Vector Magnitude

The length or size of the vector, calculated as the square root of the sum of its squared components.

Velocity Variation

Difference between the final velocity and the initial velocity of a body during a time interval.

Velocity-Time Graph

Visual representation where the slope of the straight line indicates the value of the movement’s acceleration.

Venus

Second planet in the Solar System, known for its dense carbon dioxide atmosphere and high temperatures.

Vertex

The joining point where two sides of a polygon meet and where the angle is formed.

Vertical Displacement

Change in position of an object measured along the axis perpendicular to the horizon.

Vertical Rectilinear Trajectory

Path followed by an object in ascent or descent perpendicular to the ground following the direction of gravity.

Virtual Focal Point

Point from which light rays appear to originate after being scattered by a concave lens.

Virtual Image

Image formed by the extension of reflected rays that appears to be located behind the mirror.

Voltage (Tension)

Electric potential difference between two points in a circuit that drives the movement of charges, measured in Volts (V).

Voltage Divider

Configuration of resistors in series that distributes the total source voltage proportionally to each resistor.

Voltage Drop

Decrease in electric potential when passing through a resistive component due to the energy consumption of the charges.

Voltmeter

Instrument used to measure the potential difference between two points; it is always connected in parallel.

Water

Inorganic compound formed by two hydrogen atoms and one oxygen atom (H₂O), essential for all known life forms.

Water Vapor

Water in a gaseous state that mixes with the air; it is the main driver of cloud formation and meteorological phenomena.

Watt

Unit of power representing the transfer or consumption of one joule of energy per every second of time.

Wave

Perturbation that propagates carrying energy without net transfer of matter, measured in joules (J) for the energy carried.

Wave amplitude

Maximum displacement of the perturbation from its equilibrium position or central value.

Wave Function (Ψ)

Mathematical entity containing probabilistic information about the position and state of a quantum particle.

Wave Reflection

Change in direction of a pulse upon reaching the end of the string, potentially inverting its phase depending on whether the end is fixed or free.

Wave-Particle Duality

Fundamental concept stating that light exhibits properties of both electromagnetic waves and discrete particles.

Wavelength

Physical distance between two consecutive points that are in the same state of vibration, measured in meters (m).

Weight

Gravitational force acting on a mass and varies by location. The SI unit of measurement is the Newton (N) and in the technical system the kilopond (kp).