18 Used to（do）过去经常

Used to do：过去常常做某事，但现在不做了。
Be used to doing： 习惯或已经适应做某事。

used to do:
1.过去规律性发生的事情，现在已经不再发生了:
Diane used to travel a lot. These days she doesn't go away so often.
I used to play tennis a lot, but I don't play very often now.
Do you go to the cinema very often? Not now, but I used to.
2.过去是事实，现在已经不是了:
This building is now a furniture shop. It used to be a cinema.
I've started drinking coffee recently. I never used to like it before.

I used to do something是过去时态，没有现在时形式。
He used to smoke.的现在时态是He smokes.
We used to live in a small village, but now we live in London.
一般疑问句形式: Did you use to…?
Did you use to eat a lot of sweets when you were a child?
否定句形式:didn't use to或者used not to
I didn't used to like him./I used not to like him

比较I used to do和 I am used to doing
I used to live alone.我过去曾经独居，但是现在不了。
I am used to living alone.我很适应独居的生活。