theo ‧ ry S2 W1 AC /ˈθɪəri $ ˈθiːəri/ BrE AmE noun ( plural theories )
[ Word Family: noun : ↑ theorist , ↑ theory , ↑ theorem , theoretician; verb : ↑ theorize ; adverb : ↑ theoretically ; adjective : ↑ theoretical ]
[ Date: 1500-1600 ; Language: Late Latin ; Origin: theoria , from Greek , from theorein 'to look at' ]
1 . [countable] an idea or set of ideas that is intended to explain something about life or the world, especially an idea that has not yet been proved to be true ⇨ theoretical
different theories about how the brain works
Darwin’s theory of evolution
the theory that light is made up of waves
2 . [uncountable] general principles and ideas about a subject:
Freudian theory has had a great influence on psychology.
political/economic/literary etc theory
I’m taking a course on political theory.
3 . in theory something that is true in theory is supposed to be true, but might not really be true or might not be what will really happen OPP in practice :
In theory, everyone will have to pay the new tax.
4 . [countable] an idea or opinion that someone thinks is true but for which they have no proof
Detectives are working on a theory that he knew his murderer.
• • •
▪ come up with/develop a theory
These birds helped Darwin develop his theory of natural selection.
▪ test a theory
Researchers gave workers a questionnaire to test that theory.
▪ prove a theory
No evidence emerged to prove either theory.
▪ support a theory
Modern research strongly supports this theory.
▪ disprove a theory ( also refute a theory formal ) (=show that it is wrong)
Later experiments seemed to disprove the theory.
▪ discredit a theory (=make people stop believing in it)
These latest findings discredit his entire theory.
■ ADJECTIVES/NOUN + theory
▪ a scientific theory
Scientific theories can be tested experimentally.
▪ an economic theory
His economic theory assumes that both labour and capital are perfectly mobile.
▪ a conspiracy theory (=a theory that an event was the result of secret plan made by two or more people)
A variety of conspiracy theories question the official account of President Kennedy’s assassination.
▪ a pet theory (=a personal theory that you strongly believe)
Each of them had his pet theory on what had caused the uprising.
▪ the theory of evolution/relativity etc
According to the theory of relativity, nothing can travel faster than light.