the·o·rem /ˈθiərəm, ˈθɪ(ə)rəm/
  定理,法則
  theorem
  定理
  theorem
  定理
  The·o·rem n.
  1. That which is considered and established as a principle; hence, sometimes, a rule.
     Not theories, but theorems (░), the intelligible products of contemplation, intellectual objects in the mind, and of and for the mind exclusively.   --Coleridge.
  By the theorems,
  Which your polite and terser gallants practice,
  I re-refine the court, and civilize
  Their barbarous natures.   --Massinger.
  2. Math. A statement of a principle to be demonstrated.
  Note: ☞ A theorem is something to be proved, and is thus distinguished from a problem, which is something to be solved. In analysis, the term is sometimes applied to a rule, especially a rule or statement of relations expressed in a formula or by symbols; as, the binomial theorem; Taylor's theorem. See the Note under Proposition, n., 5.
  Binomial theorem. Math. See under Binomial.
  Negative theorem, a theorem which expresses the impossibility of any assertion.
  Particular theorem Math., a theorem which extends only to a particular quantity.
  Theorem of Pappus. Math. See Centrobaric method, under Centrobaric.
  Universal theorem Math., a theorem which extends to any quantity without restriction.
  The·o·rem, v. t. To formulate into a theorem.
  ◄ ►
  theorem
       n 1: a proposition deducible from basic postulates
       2: an idea accepted as a demonstrable truth