n. the cardinal number that is the sum of three and one
s. being one more than three
num. 四, 四个
[机] 四冲程循环
1. I have four apples in my bag.
我的包里有四个苹果。
2. There are four seasons in a year.
一年有四个季节。
3. She invited four friends to her birthday party.
她邀请了四个朋友参加她的生日派对。