将英语句子改为长句的方法包括使用连接词、关系代词、分号、破折号和括号。这些方法可以增强表达能力，使句子更加流畅和自然。但是，长句并不一定比短句好，应根据具体情况选择合适的句子长度来表达自己的意思。
1. 使用连接词
使用连接词可以将简单句或复合句连接起来，组成一个长句。例如：and, but, or, so, yet等。例如：The weather was cold. We decided to stay indoors. 可以改成：The weather was cold, so we decided to stay indoors.
2. 使用关系代词
关系代词可以用来连接两个简单句或复合句，使其成为一个长句。例如：who, whom, whose, that, which等。例如：The man is my neighbor. He often helps me. 可以改成：The man who often helps me is my neighbor.
3. 使用分号
分号可以将两个相互关联的简单句或复合句分开，使其成为一个长句。例如：I like to read. My sister likes to paint. 可以改成：I like to read; my sister likes to paint.
4. 使用破折号
破折号可以将两个相互关联的简单句或复合句连接起来，形成一个长句。例如：She was late for work. She missed an important meeting. 可以改成：She was late for work - she missed an important meeting.
5. 使用括号
括号可以用来插入一些额外的信息，使其成为一个长句。例如：Tom is a doctor. He works at the hospital. (He is very busy.) 可以改成：Tom, who is very busy, is a doctor who works at the hospital.
