theory

noun

(sciences) A coherent statement or set of ideas that explains observed facts or phenomena and correctly predicts new facts or phenomena not previously observed, or which sets out the laws and principles of something known or observed; a hypothesis confirmed by observation, experiment etc.

A description of an event or system that is considered to be accurate.

(uncountable) The underlying principles or methods of a given technical skill, art etc., as opposed to its practice.

(informal) A hypothesis or conjecture.

(chess and similar games) The standardization and study of fixed sequences of moves, especially in the opening phase of a game.

(mathematics) A field of study attempting to exhaustively describe a particular class of constructs.

(countable, logic) A set of axioms together with all statements derivable from them; or, a set of statements which are deductively closed. Equivalently, a formal language plus a set of axioms (from which can then be derived theorems). The statements may be required to all be bound (i.e., to have no free variables).

(obsolete) Mental conception; reflection, consideration.

Roots

theoreotheor- · Greek · look at, contemplate

Synonyms for theory

hypothesisn notionn suppositionn supposaln premisen conjecturen assumptionn idean

Synonyms & related words for theory

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Words related to theory

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Synonyms for theory

Common synonyms for theory include hypothesis, notion, supposition, supposal, premise, conjecture, assumption, idea — words that share a close meaning. Hover or tap any word on the map for its definition and part of speech.

Where does theory come from?

The word theory breaks down into one root of Greek origin: the root theor-, from Greek theoreo (“look at, contemplate”). Explore each root to see other English words built from the same source.