at

prep. 在

I'm good at it.
我做这个很在行。
I watch TV till ten at night.
我晚上看电视看到10点。
There is very little profit in selling newspapers at present.
现在卖报纸利润很少。
I have engaged a room at this hotel.
我已经在这个旅馆里预订了一个房间。
At 20 years of age the will reigns; at 30 the wit; at 40 the judgement.
20岁我们按意愿做事；30岁我们凭智慧做事；40岁我们靠判断做事。
The airplane flies at 900 kilometers an hour.
飞机以每小时900公里的速度飞行。
Please don't laugh at him.
请不要嘲笑他。
I met him at the bus stop.
我在公共汽车站遇到他的。

名词复数:at

名词 at:

a highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium
同义词：astatine, atomic number 85
100 at equal 1 kip in Laos