forget doing 忘记做过某事 (已做)
forget it 算了吧，别再提了，让它去吧; 绝对不行
forget to do 忘记要去做某事 (未做)
forgive sb. for sth. 原谅某人(做了)某事
form the habit of doing 养成做……的习惯
free from 不受……影响的，免于, 没有
free of 无……的；摆脱了……的
free of charge 免费
frighten sb. into doing sth. 恐吓某人做某事，吓唬某人做某事
from across 从……的另一边, 来自……各地的
from beginning to end 从头至尾
from behind 背后, 从后面, 从……后面
