theory

A basic idea or law that explains how something works

A belief or rule that a group accepts as true

A set of ideas about what reality is and why it exists

A set of ideas about life, knowledge, or right and wrong that people accept and follow

Something that can be shown to be true, not an opinion

According to an idea or rule, but not always true in real life

Belief that secret groups control events without real proof

An idea that tiny vibrating strings make different particles and forces

A scientific idea that space and time are linked and change with motion and gravity

A tested explanation of how nature works, supported by many experiments and facts

The idea that living things change over time by natural selection

A theory in physics that says some things like energy exist only as small, separate amounts

A set of ideas that explain how goods, services, and money move in an economy

A scientific idea that says space and time change depending on speed and gravity

Study of how people choose actions when they compete or cooperate

An idea that the universe began when a hot, very dense point expanded quickly

A set of ideas about how a country or society should be governed

A single idea that explains all forces and matter in the universe

An idea that all objects pull on each other, more when they are heavier and closer

An idea in physics that explains forces and particles as things spread through space and time, like gravity or electricity

A scientific idea by Einstein that space and time depend on how fast something moves

Part of math that studies chance and random events

A scientific idea that says gravity happens because space and time bend

The political belief that if one country becomes communist, nearby countries will fall like dominoes

Study of how to measure, store, and send information with little loss

The study of sets, groups of things, and how they relate

An idea that infectious diseases are caused by tiny organisms like bacteria or viruses

A theory by Albert Einstein that explains gravity as the bending of space and time

A way of studying groups of parts that work together in many fields

A scientific idea that space and time change with speed and that light has the same speed for all observers

Explains gravity as the bending of space and time by heavy objects

An idea most experts do not accept and that has little evidence

A branch of physics explaining how very small particles and fields interact

Study of how people send and receive messages through media like newspapers, radio and television

The idea that light and energy move as waves rather than particles

A scientific idea that all matter is made of tiny particles called atoms

A 1905 Einstein theory saying time and space change because light's speed is always the same

A part of math that studies chance and how likely events are

A part of math that studies how things combine and their rules

A set of ideas about life, knowledge, or right and wrong that people accept and follow

A theory saying electrons orbit the nucleus in fixed energy levels and give off light when they change energy

An idea that explains patterns in how people live and act in society

A scientific idea that objects with mass pull on each other more strongly when they are heavier and closer

An idea that the universe stays the same overall because new matter is made as galaxies move apart

A scientific idea about how objects pull each other, with larger objects pulling more and pull weakening with distance

Study of events that look random but show hidden patterns

Population often grows faster than food and other resources, causing shortages

An early form of string theory that describes only bosons, a type of particle, and needs 26 dimensions

An idea in physics that gases are made of tiny moving particles that cause pressure and temperature

A scientific theory saying any two objects pull each other more if heavier and less as they get farther apart

Study of how people choose actions when each choice affects others

A scientific idea that explains how traits pass from parents to children in living things

A field that studies how to find out about a group or process from data

A part of algebra that uses symmetry to study when polynomial equations can be solved

A scientific idea that light moves as waves and makes bright and dark patterns

The idea that the mind works by linking ideas or past experiences

An idea that says cells make up all living things

Long periods of little change followed by short, fast bursts of new species forming

A physics idea that light moves at the same speed and time and space change for moving people

An idea that explains gases as made of tiny particles moving in all directions

A scientific idea that explains the weak force that makes some atoms change into other atoms

A theory that says all matter is made of tiny particles that cannot be divided called atoms

A scientific idea that the universe began in a huge explosion from one tiny hot point and is still expanding

A theory that light is made of tiny particles

A scientific idea that Earth's outer layer of rock moves in large plates and causes earthquakes, volcanoes and mountains

A strange idea that is unlikely and has no proof

The idea that parts must be seen together to understand the whole

An explanation of how acids and bases split into charged particles in water

An idea that new matter is created so the universe keeps the same density as it expands

The idea that light is a stream of tiny particles rather than a wave

The idea that temperature goes up when particles move faster

Acids break into hydrogen ions and bases into hydroxide ions in water, forming salt and water

A theory that says all matter is made of very small parts called atoms

Substances that are weak acids or bases and that have charged and uncharged forms with different colors

A chemistry idea that acids, bases, and salts split into charged particles in water

A rule that explains why dyes used to show acid or base change color when their two forms look different

A scientific idea that living things slowly change and share common ancestors

A wrong idea that a tiny fully formed body in an egg or sperm just grows bigger

A scientific idea that light travels as waves rather than particles