它们之间的主要区别如下：

answer为“辩护”，是最通用词汇，在司法程序中，指被告对原告指控的第一次答辩或提出相反陈述。在一般诉讼中，其可指答复书面质询的正式书面陈述；在离婚诉讼中为被告人对离婚请求的答复；在宗教法院中其被称为申辩，但也要求有本人的答复。

 “ A defendant's first pleading that addresses the merits of the case, usu. by denying the plaintiff's allegations. An answer usually sets forth the defendant's defense and counterclaims. ”Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 90，West Group (1999).

如：

As for traffic cases where charges are to be laid cover more serious traffic offences, should the

defendant, who is usually on bail, fail to appear before the Court to answer the charge(s), the Magistrate may issue a warrant of arrest against the defendant.

至于以起诉方式检控的交通个案涉及较严重的交通罪行，假如被告人在保释期间没有到法庭席前就控罪答辩， 裁判官可对被告人发出逮捕令。

reply为“答复”，用于指原告对被告答辩时提出的问题或反诉所作的答复和反驳；或对第三方当事人的辩护的答复和反驳。

In the case mentioned in parts (b) and (c) of the reply, the Court of Appeal has ruled that the plaintiff is entitled to the benefits attributable to the period after his discharge from bankruptcy.

根据答覆第（二）及第（三）部分提及的案件，上诉法庭已判定原告有权获得破产解除后所累积的公积金。

rejoinder为“第二次辩护”，指普通法诉讼中被告对原告之reply的辩驳。如：

By an order of 12 March 2010, the Court authorized the submission of a reply by the former Yugoslav Republic of Macedonia and a rejoinder by Greece.

法院于 2010 年 3 月 12 日发出命令，批准前南斯拉夫的马其顿共和国提出答辩状、希腊提出复辩状。

因此，可以看出，这三者的逻辑关系大致如下：

原告指控——被告答辩（answer）——原告答复被告在答辩时提出的问题和反驳（reply）——被告再次对原告进行反驳（rejoinder）。