这四个单词中，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; 二是"从犯"，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，此时其等同accessory。

Accomplice and Confederate: A person who is in any way concerned with another in the commission of a crime, whether as principal in the first or second degree or as an accessory. A person knowingly, voluntarily, and intentionally unites with the principal offender in committing a crime and thereby becomes punishable for it. 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.如：

Without the corroboration rule, judges would be able to exercise their discretion to deal with the credibility of accomplice witnesses in the same manner as they deal with credibility generally.

撤销这项确证规则后，法官便可行使酌情权，利用处理证供可信程度的一般方法，去处理共犯证人证供的可信程度。

abettor则指直接参与犯罪者，故其应为"共犯"，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)。

Abettor: An abettor is an accomplice or confederate who is present and who participates in the execution of a crime. 如：

The general provisions (sections 19 to 21) of the Penal Code stipulate that parties to a crime include the perpetrator and the co-actor (parties to a crime), the abettor and the accomplices (conspirators).

《刑法典》总则(第 19 至 21 条)规定，犯罪方包括实施方和共同行为方(参与犯罪者)、教唆方和从犯(共谋)。

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 thefact (事后从犯)。

Accessory :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 caled accessory after the fact.