尽管两单词经常交替使用，但它们仍然具有一定差异。在日常英语中，ambiguity (含糊）多指因意思不明确而可作两种选择，因而严格地说它更多是指“模棱两可”；而vagueness (模糊）所指的选择范畴则更为广泛[1]。但在法律解释领域，ambiguity有所扩大，用于指因意思不明确而有多种（而不仅是两种）选择[2]。但这并不意味它便等同vagueness。事实上，两者实质性的区别在于法律文本中的ambiguity纯粹是一种语病，属于立法技术瑕疵，是法律起草人必须避免的现象；而vagueness 却是法律语言的一大特征， 常是立法者在无法或不便作精确（precise)规定时，主动或有意做模糊表达的结果，目的是给法官等留下一定自由裁量的空间，如in the reasonable time (在合理的期限之内）便是一种vagueness而非ambiguity[3]。同样，我国刑法中常出现的“数额特别巨大”或“情节特别严重”等表述也都是属于“模糊”而非“含糊”词语，都是立法者在不愿或无法进行精确确认时留给法官进行自由裁量的典型范例，具体实践中常由最高人民法院的司法解释来确认什么是“数额巨大”或“数额特别巨大”，以及什么是“情节严重”或“情节特别严重”等。

此外，ambiguity所导致的不确定性常起支配和主导作用，即起“不是/则是的作用”，因而尤其要小心避免。而vagueness的不确定性却只与边缘或轻微问题相关[4]。
 
[1]“Ambiguities ( which involve an either/or choice) and vagueness (which involve a widely-ranging choice) as well as any mistakes should be carefully preserved. ” Cf. Cornelia E. Brown ( Hamilton College) , Riding the Waves of Fortune ： Translating Legislation of the Successor Soviet Republics, at p. 68, John Benjamins Publishing Company (1995).

[2]“In ordinary language this term is often confined to situation in which the same word is capable of meaning two different things，but, in relation to statutory interpretation, judicial usage sanctions the application of the word ambiguity to describe any kind of doubtful meaning of words, phrases or longer statutory provisions. ” Cf. Bryan A. Gamer, Black's Law Dictionary, at p. 79，7th edition, West Group (1999).

[3] Cf. Thomas R. Haggard, Legal Drafting, at p. 250, West Group (1996).

[4]“Ambiguity is a disease of language，whereas vagueness，which is sometimes a disease，is often a positive benefit. . . whereas ambiguity in its classical sense refers to equivocation, vagueness refere to the degree to which, independently of equivocation, language is uncertain in its respective applications to a number of particulars. Whereas the uncertainty of ambiguity in central, with an either-or challenge, the uncertainty of vagueness lies in marginal questions of degree. B Cf. Reed Dickerson，The Interpretation of Statutes，at pp. 48 ~49, West Group (1995).