这是两个非常非常容易混淆的短语，相差一个be动词，意思却截然不同。
Used to我们来看两个例句，猜猜对一个人的描述：
Dennis smoked when he was 23-year-old.
Dennis23岁的时候就抽烟了。
Dennis stopped smoking two years ago. He doesn't smoke any more.
Dennis两年前停止吸烟了，而且再也没有抽过。
所以，我们总结：
Dennis used to smoke.
Dennis曾经吸过烟。
简而易见，used to 的表明的要素就两点：
1.过去曾经做过（经常性的）
2.现在已经不做了或者次数减少了
我们看两个例子验证：
I used to play basketball once a week, but I don't play very often now.
我以前一周打一次篮球，但是现在不经常打了。
Do you go to the cinema very often?你经常去电影院吗？
--not, but I used to . 不，但我以前经常去。
同时，我们也可以用used to...表示“某些事物过去的观点，状态和现在已经不同”。
I used to think he was unfriendly, but now I realise he's a very nice man.
我以前觉得他不友好，但现在我意识到他是一个非常友好的人。
Jane used to have very long hair, but now she doesn't.
Jane以前是留非常长的头发，但是现在不是了。
跟used to 只差了一个be动词，意思差别可大了。我们来看看例子描述：
Frank lives alone. He doesn't mind this because he has lived alone for 15 years.
Frank独自一个人住，他并不介意这个，因为他已经独自一个人住了15年了。
从而，我们得出结论：
Frank is used to it. He is used to living along.
他习惯这样子，他习惯自己一个人住。
我们用be used to 表明“习惯于......”, 有两种结构：
be used to something 习惯于某事/某物
be used to doing something 习惯于做某事
I bought some new shoes. They felt a bit strange at first because I wasn't used to them.
我买了一些新鞋，刚开始穿起来有些奇怪，因为我还没有习惯它们。
I got a new job,and I must get up much earlier now, I found it's difficult because I'm not used to getting up so early.
我换了份新工作，现在必须早起很多，然而我发现这很困难，因为我不习惯起得如此早。
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