“Principal”这个词很常见，但是在不同语境下表达的含义有所不同，需要注意区分。比如，作形容词时，常用于表示“最重要的”，如“principal shareholder”（主要股东）。作名词时，在学校中表示“校长”；在金融领域，表示“本金”，固定搭配有“principal and interest”（本金和利息）；在代理关系中，表示“委托人”，如“principal and agent”（委托人和代理人）。此外，在法律领域中，“principal”可以用于表示“主犯”，指实施犯罪行为或在现场帮助或唆使他人实施犯罪行为的罪犯，与从犯〔accessory〕相对，此处“principal”还可以作形容词与“offender”或“criminal”连用表示“主犯”。

例句1

原文：

In the case of every felony, every principal in the second degree and every accessory before the fact may be indicted, tried, convicted and punished in all respects as if a principal in the first degree; provided, however, that except in the case of a killing for hire under the provisions of subdivision A 2 of §18.2-31 or a killing pursuant to the direction or order of one who is engaged in a continuing criminal enterprise under the provisions of subdivision A 10 of §18.2-31 or a killing pursuant to the direction or order of one who is engaged in the commission of or attempted commission of an act of terrorism under the provisions of subdivision A 13 of §18.2-31, an accessory before the fact or principal in the second degree to an aggravated murder shall be indicted, tried, convicted and punished as though the offense were murder in the first degree.

（来源：Code of Virginia第18.2编第2章第18.2-18节）

译文：

就每项重罪而言，各二级主犯和各事前从犯可犹如一级主犯一样在各方面受到公诉、审判、定罪和惩罚；但是，第18.2-31节第A2款项下的雇佣杀人，或第18.2-31节第A10款项下的根据从事持续性犯罪活动之人的指示或命令进行杀人，或根据第18.2-31节第A13款项下的根据从事实施或企图实施恐怖主义行为之人的指示或命令进行杀人除外，犯有严重谋杀罪的事前从犯或主犯应犹如犯有一级谋杀罪一样受到公诉、审判、定罪和惩罚。

例句2：

Any person who aids, abets, counsels, procures or suborns another person to commit an offence against this Part shall be liable to be proceeded against, indicted, tried and punished as if he were a principal offender.

任何人协助、教唆、怂使、促致或唆使他人犯本部的罪行，可予以起诉、公诉、审讯及惩处，犹如他是主犯一样。

（来源：《刑事罪行条例》（香港法例第200章）第38条第二款）

例句3：

原文：

组织、领导犯罪集团进行犯罪活动的或者在共同犯罪中起主要作用的，是主犯。

三人以上为共同实施犯罪而组成的较为固定的犯罪组织，是犯罪集团。

对组织、领导犯罪集团的首要分子，按照集团所犯的全部罪行处罚。

对于第三款规定以外的主犯，应当按照其所参与的或者组织、指挥的全部犯罪处罚。

（来源：《中华人民共和国刑法》第二十六条）

译文：

A principal criminal refers to any person who organizes and leads a criminal group in carrying out criminal activities or plays a principal role in a joint crime.

A criminal group refers to a relatively stable criminal organization formed by three or more persons for the purpose of committing crimes jointly.

Any ringleader who organizes or leads a criminal group shall be punished on the basis of all the crimes that the criminal group has committed.

Any principal criminal not included in Paragraph 3 shall be punished on the basis of all the crimes that he participates in or that he organizes or directs.

来源：

《元照英美法词典》；

www.elegislation.gov.hk；

https://law.lis.virginia.gov/vacode/title18.2/chapter2/section18.2-18/