An onlooker is someone who watches something happen and does not take part. A crowd around a street musician, people standing at a fire, neighbours watching an argument in the road — those people are onlookers.

An onlooker is一個onlooker是 someone一個人 who watches something happen看著事情發生 and does not take part但不參與其中。A crowd around a street musician像是圍在街頭藝人旁邊的一群人、people standing at a fire站在火災旁邊看的人、neighbours watching an argument in the road鄰居在路上看人吵架——those people are這些人都是 onlookersonlookers（旁觀者）。

The word is fairly neutral. It does not praise you and it does not attack you; it just says you were looking, not doing. Though actually, it can feel a little cool, as if you stayed outside on purpose.

The word is這個詞算是 fairly neutral相當中性的。It does not praise you它不是在誇你 and it does not attack you也不是在攻擊你；it just says它只是說 you were looking, not doing你只是在看，沒有在做。Though actually不過其實，it can feel a little cool它可能給人一點冷淡的感覺，as if you stayed outside on purpose好像你是故意站在外面一樣。

A bystander is simply there. An onlooker is there and watching. A spectator has usually come to watch a show or a game; an onlooker often just stops because something is going on.

A bystanderbystander（在場的人） is simply there只是剛好在場而已。An onlookeronlooker is there and watching則是在場、而且正在看。A spectatorspectator（觀眾） has usually come to watch a show or a game通常是特地來看表演或比賽的；an onlookeronlooker often just stops常常只是剛好停下來 because something is going on因為有事情正在發生。

It is everyday English, not fancy, not slang.

It is這是 everyday English日常英文，not fancy不是什麼花俏的詞，not slang也不是俚語。