1、in可以用作介词，表示在...里面的意思，例如，Is Mark still in bed? 马克还在睡觉吗？I got stuck in a traffic jam for half an hour. 我堵车堵了半个小时。
2、in有到…里面的意思，看例句，Put the milk back in the fridge when you've finished with it. 喝完牛奶后把它放回冰箱。They threw him in the swimming pool. 他们把他扔进了游泳池。
3、in用的较多的是表示在…期间，例如，I started working here in 2009. 我从2009年开始在这儿工作。
4、This is the first cigarette I've had in three years. 这是我3年来抽的第一支烟。
