助动词或辅助动词是帮助形成动词短语但不能独立做谓语使用的动词。 助动词具有语法意义，但没有词汇意义，不可单独作谓语。

有四个基本助动词组：

To Be

这个辅助动词用于渐进时态和被动语态：

进行时：

• You are kicking.
• You were kicking.
• You have been kicking.

被动语态：

• You are kicked.
• You were kicked.
• You have been kicked.

To Have

这个动词在完成时用作辅助词：

• I have finished my paper.
• I had finished my paper.
• I have been finished with my paper.

情态助动词

这些辅助因素影响动词的情绪; 也就是说，它们确定动词是事实，欲望，可能性还是命令。 它们最常用于表示自由度或严重程度。

最常见的情态动词: will, shall, can, may, need (to), dare, would, should, could, might, must, ought (to)

• 能力: I can run.
• 必要性: I must run.
• 义务: I ought to run.
• 允许: I may run.

To Do

当句子的主要动词需要辅助辅助时，使用此动词，但没有其他适合的动词。 它经常用于问题，否定或强烈的陈述：

• Does he drive?
• He drives, doesn't he?
• Despite his flat tire he does drive.