pro·vi·so /prəˈvaɪ(ˌ)zo/
  但書;條件
  Pro·vi·so n.; pl. Provisos   An article or clause in any statute, agreement, contract, grant, or other writing, by which a condition is introduced, usually beginning with the word provided; a conditional stipulation that affects an agreement, contract, law, grant, or the like; as, the contract was impaired by its proviso.
  He doth deny his prisoners,
  But with proviso and exception.   --Shak.
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  proviso
       n : a stipulated condition; "he accepted subject to one
           provision" [syn: provision]
       [also: provisoes (pl)]