和used有关的四种表达式：
1.used to do sth 过去常常做某事（暗示现在已经不再做了。used是半情态动词，否定句或疑问句既可以遵循情态动词的原则也可以遵循实意动词原则。used to do sth. 否定句句既可以是didn't use to do sth.也可以是usedn't to do sth.疑问句形式既可以是Did+主语+use to do sth?也可以是Used+主语+to do sth?）
He used to go for a walk after dinner when he was young.
他小时候，饭后常常回去散步。(暗示现在已不散步了。)
注意:A,used to与often, always, never等副词连用时，既可以置于used之后，也可置于used之前，例如:She always used [used always] to be afraid of cats. 她过去老是怕猫。
B，used to do sth表示“过去常常做”与would do sth的区别是表示“过去的常常做的动作”时，常用would do sth.其它都用used to do sth.
例如:when he was a child ,he would go camping in the open air.当他是孩子时，经常到户外宿营。
C，there used to be sth+地点，表示某处过去常常有某物，暗示现在已不存在。
There used to be a temple on the top of Tian zhong Hill.(天中山顶过去有一座寺庙。)
2.get/be used to doing sth.（现在）习惯做某事=be /get accustomed to doing sth.
I get used to reading English every morning.
我习惯每天晨读英语。
3.sth be used to do 某物被用来做某事=be used for doing sth.
Scissors are used to cut things.
人们用剪刀来剪东西。
4.used 表示二手的，旧的(=second-handed)
I bought a used car yesterday.
昨天我买了一辆二手车。
