The Theory of Everything is an autobiographical sports novel.
 There are theories in many and varied fields of study, including the arts and sciences
In the same sense, but more specifically, the word theory is an extensive, structured collection of theorems, organized so that the proof of each theorem only requires the theorems and axioms that preceded it (no circular proofs), occurs as early as feasible in sequence (no postponed proofs), and the whole is as succinct as possible (no redundant proofs)

