上述单词具有共犯或从犯的含义。其中，accomplice和confederate 的含义相近， 在美国，其有双重含义：一是“共犯”， 指与他人一起共同实施犯罪，不论其身份是主犯或从犯[1 ] ；二是“从犯”[2]，此时其主要指在策划或实施阶段，协助他人犯罪 或故意不履行法定阻止义务而旨在加速或促进犯罪的实施者， 因此，一个accomplice或confederate可能但不必一定亲自作案[3]，此时其等同accessory。abettor则指直接参与犯罪者，故其应为“共犯”[4]，如：A look-out is an abettor in a bank robbery (银行抢劫案中的放哨者是该案的共犯）:abettor也可拼写为abetter，其也称为 principal in the second degree (二级主犯）。相比之下，accessory则为“从犯”，与主犯（principal)相对，主要指协助重罪犯犯罪者。它分为两类，如果此种协助是在犯罪预备时进行，被称为an accessory before the fact (事前从犯）;如果是在罪犯之后协助罪犯脱逃，也被称为an accessory after the fact (事后从犯）[5](有关此种分类现在的区别，参见条目accessory before the fact) 。
 
[1 ]“ A person who is in any way concerned with another in the commission of a crime，whether as principal in the firet or second degree or as a accessory. " Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 16，West Group (1999).
[2 ]“A person knowingly, voluntarily, and intentionally unites with the principal offender in committing a crime and thereby becomes punishable for it. ” Id. at p. 16.
[3 ]“Person is liable as an accomplice to the crime of another if he gave assistance or encouragement or failed to perform a legal duty to prevent it with the intent thereby to promote or facilitate commission of the crime. ” Cf. The Publisher's Staff, Black's Law Dictionary, abridged 6th edition, at p. 10, West Publishing Co. (1997).
[4 ]“An abettor is an accomplice or confederate who is present and who participates in the execution of a crime. ” Cf. The Editors of the Reader’s Digest, Use the Right Word, at. p. 3, The Reader's Digest Association Proprietary Ltd. (1971 ).
[5 ]“A person who is not actually or constructively present but with criminal intent contributes as an assistant or instigator to the commission of a felony, also called accessory before the fact ”、" A person who knowing that a felony has been committed aids，assists, or shelters the offender with the intent to defeat justice，also called accessory after the fact." Cf. Linda Picard Wood，J. D.，Merriam Websters Dictionary of Law，at p. 6, Meniam-Webster, Incorporated, Springfield, Massachusetts (1996).