哀思【āi sī】
grief; mourning
[名]悲哀思念的感情

李先生去世后,大家都以各种方式表示哀思。
People expressed their mourning for the death of Mr. Lee in different ways.
唉【āi, ài】
(āi) 1. yes; well (ài) 2. alas
(āi) [叹]1、答应的声音;叹息的声音 (ài) [叹]2、表示失望或惋惜等

A:小张,电话! B:唉,来了。
A: Xiao Zhang! Here is a phone call for you! B: Yes, I am coming.

唉,要是我们队没有犯规就好了。
Alas! If only our team had not broken the rules.
挨【ái,āi】
(āi) 1. get close to 2. touch (ái) 3. suffer; endure
(āi) [动]1、靠近,紧接着 2、触,碰,靠 (ái) [动]3、遭受,忍受;消磨时间

从地图上可以看出,美国紧挨着加拿大。
The USA is next to Canada on the map.

奶奶挨了一下孩子的手,孩子就笑了。
The child smiled when the grandma touched his small hand.

在那些艰苦岁月,挨饿是常有的事。
People often suffered from hunger in those hard days.