助动词是一类没有词义的词，用于与连系动词或实义动词的原形或分词一起构成谓语动词的时态、语态、语气及否定、疑问和强调形式。常见的助动词包括be, do, have, will, shall，would等的各种形式。
- Be: 用于构成进行时态和被动语态，也可用于表示状态或身份。例如：
- I am a teacher. (我是一名老师。)
- The book was written by a famous author. (这本书是由一位著名作家写的。)
- She is reading a book. (她正在看书。)
- Do: 用于构成疑问句和否定句，也可用于强调句子中的某个部分。例如：
- Do you like pizza? (你喜欢披萨吗？)
- I don’t know the answer. (我不知道答案。)
- Do come in! (请进！)
- Have: 用于构成完成时态，也可用于表示拥有或经历。例如：
- I have finished my homework. (我已经完成了作业。)
- She has a cat and a dog. (她有一只猫和一只狗。)
- He has been to Japan twice. (他去过日本两次。)
- Will: 表示将来时态，will可用于任何人称。例如：
- I will go to the party tomorrow. (我明天会去参加聚会。)
- He will be twenty-five years old next month.（他下个月将是二十五岁。)
- The weather forecast says that there’ll be heavy rain tomorrow.（天气预报明天有大雨。)
- Shall: 用于表示将来时态，只能用于第一人称。例如：
- I shall be eighteen next March.（明年三月我将十八岁了。)
- We shall arrive tomorrow.（我们将于明日到达。)
- Don’t worry. We shall tell you all about it.（你别担心。我们都会告诉你的。)
- Would: 表示过去将来时态，或用在虚拟条件句中。例如：
- He said he would come tomorrow. (他说他明天会来。)
- He said that he would always remember that day.（他说他将永远记住那一天。)
- If I had more time, I would visit Paris. (如果我有更多时间，我会去巴黎旅游。)