theory

UK/ˈθɪə.ɹi/US/ˈθɪ.ɹi/

nounB23 meanings Very common — you will meet it every day · #1,144 of 15,258leans written

Other forms: theories

A theory is an explanation of why things happen the way they do — one that has been tested, argued over, and is still standing. Gravity, evolution, plate tectonics: theories in the strong sense.

In everyday talk the word is much weaker. I have a theory about why he left early is a hunch with no testing behind it, and that gap causes real trouble: when someone says evolution is only a theory, they are using the kitchen sense of a laboratory word. Theory also means the body of ideas behind a practice — music theory, colour theory, the theory test you sit before you are allowed to drive. In theory means on paper, and it sets up a but: in theory the bus takes twenty minutes. The adjective is theoretical and the verb is theorise.

Definitions of theory

1nounexplanationAn explanation of how something works that has been tested hard enough to rely on.B2~18%
“Darwin's theory explains how species change over time.”
2nountheoryAn idea or guess about why something happened, with little to back it up.B1~9%
“My theory is that he forgot the whole thing.”
3nounsetThe set of principles behind a subject or skill, as opposed to doing it.B2~73%
“She knows the theory but has never driven in traffic.”

Shares are an estimate: a language model read 11 sentences found in the wild and placed 11 of them on a sense — a count of our sample, not a measurement of English.

theory is an explanation.

Phrases it lives in

in theory — the way something should work, rather than the way it does

Where it comes from

Latin
theōria
Middle French
théorie
English, today
theory

Borrowed from Middle French théorie, from Latin theōria.

Etymology from Wiktionary, CC BY-SA

Practised in Science & Space, Logic & Argument

Practise this word

theory in the wild

Belief in a single conspiracy theory is often associated with belief in other conspiracy theories.
Conspiracy theory
The theory was first set out in detail in Darwin's book On the Origin of Species.
Evolution
Set theory is the branch of mathematical logic that studies sets, which can be informally described as collections of objects.
Set theory
Thus, string theory is a theory of quantum gravity.
String theory
String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics.
String theory

1 / 5

From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

Related words

the théorie family

theory

theory — used about once every 116 pages · #1,144 · point at the bar for the others

music theory

Definitions of theory

1nounexplanationAn explanation of how something works that has been tested hard enough to rely on.B2~18%

“Darwin's theory explains how species change over time.”

2nountheoryAn idea or guess about why something happened, with little to back it up.B1~9%

“My theory is that he forgot the whole thing.”

3nounsetThe set of principles behind a subject or skill, as opposed to doing it.B2~73%

“She knows the theory but has never driven in traffic.”

Shares are an estimate: a language model read 11 sentences found in the wild and placed 11 of them on a sense — a count of our sample, not a measurement of English.

theory is an explanation.