- Obs. a mental viewing; contemplation
- a speculative idea or plan as to how something might be done
- a systematic statement of principles involved: the theory of equations in mathematics
- a formulation of apparent relationships or underlying principles of certain observed phenomena which has been verified to some degree
- that branch of an art or science consisting in a knowledge of its principles and methods rather than in its practice; pure, as opposed to applied, science, etc.
- popularly a mere conjecture, or guess
Origin of theoryfrom French or LL: French théorie from Late Latin theoria from Classical Greek the?ria, a looking at, contemplation, speculation, theory from the?rein: see theorem