在英语中"be"（助动词）和"for"（介词）都有多种用法和功能，但它们之间有明显的区别。下面是"be"和"for"的基本用法和区别：

1. "be"：

- 用于一般现在时的主语人称和数：I am, you are, he/she/it is, we/you/they are.

- 用于进行时态：I am eating, you are eating, he/she/it is eating, we/you/they are eating.

- 用于被动语态：He was hit, she was kissed, it was eaten, we were asked.

- 用于无人称句和否定句：You are not sleepy. We are not tired.

2. "for"：

- 表示原因：He was late for the train. She was sick for a few days.

- 表示目的：He bought a book for his son. We went for a walk in the park.

- 表示时间或距离：It's ten minutes for the bus. They traveled for a week.

- 表示对象或参考点：He drove the car for me. The book is on the shelf.

总结：

- "be"是一个助动词，用于构成进行时态、被动语态和无人称句等。

- "for"是一个介词，用于表示原因、目的、时间、距离、对象或参考点等。

在句子中"be"通常与主要谓语动词一起使用，而"for"与其他动词或名词一起使用。了解"be"和"for"的用法和功能有助于更好地理解和使用英语句子。