looks当外貌时必须是复数吗

是的。当look作名词“面容，美貌”使用时，无论同单数还是复数词语连用时，都必须使用复数形式looks。所以无论几个人都使用looks。例如: Don't judge a man by his looks. The twins have good looks.

Look短语

1、look about [around]

(1) 环顾四周。

如：The man kept looking about.这个人不停地环顾四周。

(2) 随便看，到处看。

如：A：What can I do for you, madam?夫人，想买什么吗?

B：No, I’m just looking around.不是，只是随便看看。

(3) 到处寻找。

如：I’m looking about for a house.我在找一座房子。

(4) 仔细考虑。

如：Look about carefully before making the decision.先仔细考虑，然后再作决定。

2、look after 照顾，照料，关心。

如：I can look after myself.我能照顾自己。

Who is looking after the luggage?谁在照看行李?

3、look at

(1) 看……，注视……。

如：He looked at me and smiled.他望着我笑了。

Look at him jump [jumping].请看他跳。

(2) 看待。

如：That’s the way I look at it.我就是那样看待它的。

(3) 考虑（多用于含有否定意义的句子）。

如：They refused to look at my suggestion.他们拒不考虑我的建议。

(4) 检查。

如：He came to look at the drainage.他是来检查排水设备的。

4、look back

(1) 回顾，回想。

如：I still shudder when I look back on the past.想起过去，我仍然不寒而栗。

(2) 停滞，畏缩，倒退（通常用于否定句）。

如：From this time on, he never looked back.从此以后，他便不断进步。