三者均為合同法中常用詞。其中，promise是要約人向被要約人所作要約，為一種主動(dòng)的“允諾”或“許諾”[1]。而acceptance 則為 “承諾”，是被要約人（offeree)對(duì)要約（offer) 的一種認(rèn)可[2]。offer則與promise意思相同，是主動(dòng)對(duì)他人的 “要約”[3];但與promise不同的是offer可以撤銷（revocable); 而promise作為“允諾”則不能撤銷[4]。

[1]“A party's undertaking about its future conduct. " Cf. G. H. L. Fridman, The Law of Contract in Canada，2 nd edition, at p. 1，Carswell (1986). " a declaration or manifestation ，esp. in a contract, of an intention to act or refrain from acting in a specified way that gives the party to whom it is made a right to expect its fulfillment." Cf. Linda Picard Wood, J. D.，Merriam Webster's Dictionary of Law, at p. 389, Merriam-Webster, Incorporated, Springfield, Massachusetts (1996).

[2] "An agreement, either by express act or by implication from conduct, to the terms of an offer so that a binding contract is fonned. ”Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 11 , West Group (1999).

[3 ] "One person's indication to another that she or he is willing to enter into a contract with that person on certain terms. ” Cf. Daphne Dukelow, The Dictionary of Canadian Law, at p. 711, Thomson Professional Publishing; Canada (1991).

[4] Therefore, an offer is revocable, a promise is not. ” Cf. William R Arson, Some

Notes on Terminology in contract, 7 Law Q. Rev. at pp. 337, 337 (1891)