1、 表示身份、职业或身份特征：在这种情况下，"as"引导的定语从句通常放在先行词之后。例如：
- She works as a doctor, which requires a lot of patience and compassion.（她是一名医生，这需要很多耐心和同情心。）
- He is known as the best chef in town, which is quite an accomplishment.（他被誉为这个城镇最好的厨师，这是相当了不起的成就。）
2、表示原因、方式或条件：这时，"as"引导的定语从句通常放在先行词之前。例如：
- As she was tired, she decided to go to bed early.（因为她累了，她决定早点上床睡觉。）
- He ran as fast as he could to catch the bus.（他尽可能快地跑去赶公交车。）
3、表示时间：在这种情况下，"as"引导的定语从句通常放在先行词之前或之后。例如：
- I met him as I was leaving the office.（我在离开办公室的时候遇到了他。）
- He arrived at the party late, as always.（他像往常一样迟到了派对。）