Meaning of THEORY in English

THEORY

■ noun ( plural theories )

1》 a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.

↘an idea accounting for or justifying something.

2》 a set of principles on which an activity is based: a ~ of education.

↘ Mathematics a collection of propositions illustrating the principles of a subject.

Phrases

in ~ in an ideal or hypothetical situation.

Origin

C16: via late L. from Gk theōria 'contemplation, speculation'.

Concise Oxford English vocab.      Сжатый оксфордский словарь английского языка.