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

An idea that tiny vibrating strings make different particles and forces

Belief that secret groups control events without real proof

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

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

Study of how people choose actions when they compete or cooperate

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

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

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

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

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 that says gravity happens because space and time bend

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

Part of math that studies chance and random events

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

An idea that says cells make up all living things

Study of events that look random but show hidden patterns

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

A theory that light is made of tiny particles

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

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

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

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

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

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

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

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

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

The idea that temperature goes up when particles move faster

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

A strange idea that is unlikely and has no proof

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

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

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

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

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

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

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

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

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

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

Study of how people choose actions when each choice affects others

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

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

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

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

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

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

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

A scientific idea that light travels as waves rather than particles

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