“as”是英语中常见的介词和连词，用法多样。以下是其主要用法总结：
| 用法 | 例句 | 说明 |
| 作为 | She works as a teacher. | 表示身份或角色 |
| 当……时 | As he spoke, everyone listened. | 引导时间状语从句 |
| 像……一样 | He runs as fast as a horse. | 表示比较 |
| 因为 | As it was raining, we stayed home. | 引导原因状语从句 |
| 虽然 | As he is tired, he continues working. | 引导让步状语从句 |
“as”在不同语境中含义不同，需结合句子理解。掌握其常见用法有助于提高语言表达能力。
