Waiters, keen observers of humanity that they are, are catching on to this; in one poll, a full 30% said they didn't believe the job they did had any impact on the tips they received.
出自-2016年12月阅读原文
The teacher's role is more of a coach or observer.
2019年6月四级真题(第三套)阅读 Section B
柯林斯高阶英汉双解学习词典释义
N-COUNT
观察者;观测者;目击者
You can refer to someone who sees or notices something as an observer .
An observer is a person who is sent to observe an important event or situation, especially in order to make sure it happens as it should, or so that they can tell other people about it.