observers
You can refer to someone who sees or notices something as an observer.
A casual observer would have taken them to be three men out for an evening stroll.
乍一看会以为这三个男人是晚上出来闲逛的。
He argues that truly objective science is impossible: the observer affects the system he or she observes.
他争辩说完全客观的科学是不存在的:观察者会对其观察的系统产生影响。
An observer is someone who studies current events and situations, especially in order to comment on them and predict what will happen next.
Observers say the events of the weekend seem to have increased support for the opposition.
观察家们说周末事件似乎加大了对反对派的支持。
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 to tell other people about it.
The president suggested that a UN observer should attend the conference.
主席建议应该有一名联合国观察员参加该会议。