这些术语均为普通法上的术语，有“抗辩”的含义。在普通法中，demurrer为诉辩状呈送程序（pleadings)中就诉状或反 诉中的指控提交的抗辩书，主要指被告方虽承认所控事实，但 却以其法律依据不足以使诉讼成立为由而进行的抗辩[1]；其可分为普通抗辩 “general demurrer”，特殊抗辩 “special demurrer”和陈述性抗辩“speaking demurrer”三种。而confession and avoidance (也称为 avoidance、plea in confession and avoidance 或 plea of confession and avoidance)则是承认所控事实，但却提出新的附加事实以回避应负的责任[2]。如同时提出混合过失 (contributory negligence)以回避自己应当负的部分责任的抗辩则可称为是confession and avoidance。相比之下，plea则主要对所控事实或诉因进行反驳而作的抗辩；尤指在民事诉讼中被告呈送的首次 pleading 。exception 作抗辩时，常指 exceptions for insufficiency of a pleading,表示—种以诉状要件不完善或有缺陷为由的抗辩。根据现行《美国联邦诉讼法典》的规定，demurrers, pleas 和 exceptions for insufficiency of a pleading 均已被废除， 代之以起的是motion和answer;但在有些州，上述抗辩仍在适用。
    
[1]“ A pleading stating that although the facts alleged in a complaint may be true，they
are insufficient for the plaintiff to state a claim for relief and for the defendant to frame an answer. ”Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 448, West Group (1999).
[2]“ A common-law plea in which a party confesses an allegation but alleges additional facts to avoid the intended legal effect of the original allegation. ”Cf. Linda Picard Wood, J. D.，Merriam Webster's Dictionary of Law，at p. 95, Merriam-Webster, Incorporated (1996).
[3]“ In common law a pleading; any one in the series of pleadings. More particularly，the first pleading on defendant. ”Cf. The Publisher's Editorial Staff, Black's Law Dictionary, abridged 6th edition, at p. 797，West Publishing Co. (1991).