a belief, policy, or procedure forming the basis for action
Her method is based on the theory that children want to learn
the general or abstract principles of a subject
music theory
a body of theorems presenting a concise systematic view of a subject
the theory of equations
a scientifically acceptable body of principles offered to explain a phenomenon
the wave theory of light
a hypothesis assumed for the sake of argument or investigation
an unproved assumption; a conjecture
in theory
on the basis of abstract principles or under ideal circumstances, but not necessarily in practice or reality
[via late Latin from Greek theōria, from theōrein: see theorem]