1.used to(过去经常）
它表示过去常产/反复发生的动作或状态，现在不了。
(1)I used to be afraid of tigers.(我以前怕老虎）
(2)He used to take a train to get to school.（他以前常坐火车上学）
(3)Did you use to have lunch at home?（你以前经常在家吃午饭吗？）
(4)She didn't use to have curly hair.（她过去不是卷发）
(5)John used to wear glasses,didn't he?(约翰以前戴眼镜，是不是？)
它的否定形式还可以用used not to（在正式的书面语中）,同样，一般疑问句形式还可以用Used...to...?
2.be/get used to doing（习惯于做某事）
I am used to working hard all day.(我习惯了每天努力工作）
3.be used to do(被用于)
Keys are used to open and lock doors.(=Keys are used for locking doors)
4.be afraid of sth/doing sth
  be afraid to do sth
(1)You must be afraid of your headteacher.
(2)Don't be afraid of being alone.
(3)My son is afraid of going out at night.
(4)I'm afraid that you are wrong.(这里的意思表示担心，可以翻译为恐怕）
(5)Are they afraid to take the test?