theory
//ˈθɪəri//
Noun
theorySingular
theoriesPlural
1
A supposition or system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
Darwin's theory of evolution changed our understanding of biology.
2
A set of principles on which the practice of an activity is based.
She studied music theory before learning to play the piano.
3
An idea used to account for a situation or justify a course of action.
My theory is that he left early because he wasn't feeling well.
4
A collection of propositions to illustrate the principles of a subject.
She studied the theory of music composition.