Pronunciation: (thē'u-rē, thēr'ē),[key] —n., —pl.-ries. 1. a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein's theory of relativity. 2. a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.
3. Math.a body of principles, theorems, or the like, belonging to one subject: number theory. 4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory. 5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.
6. contemplation or speculation.
7. guess or conjecture.