noun
1.
a belief, policy, or procedure proposed or followed as the basis of action
an educational system that was based on the theory that men learn best by experience
Synonyms: hypothesis, supposal; compare assumption 2
Related Word: base, basis, grounds, position, premise, understanding
Antonyms: practice
2.
something taken for granted especially on trivial or inadequate grounds
her theory that the house was haunted
Synonyms: conjecture, perhaps, speculation, suppose, supposition
Related Word: guess, guesswork, surmise; feeling, hunch, impression, presentiment, suspicion
Contrasted words: assurance, certainty, knowledge