year和years的区别
years是year的复数形式，但是用法上也有区别。当表年龄时：four-year是个合成而来的形容词，只能做定语；four years是个短语，可以单纯做名词也可以做时间状语。
例句
It's a four-year course.这是一个为期四年的课程。
He has been here for four years.他在这已经待了四年了。
year old和years old
year old只能是he is only one year old.即years old的单数形式。
years old就是一岁以上的了,例如she is three years old.
year old 和 years old通常都作表语。
首先要声明绝对没有years-old的说法,因为加上连接符以后year必须用单数。
数字-year-old表示几岁,与前两个最大的区别就是它在句中只能充当定语。
例如：a three-year-old boy一个三岁大的小男孩。
但是不能说the boy is three-year-old.也就是说它不能充当表语,而要说the boy is three years old.
1、She ran away with a man called McTavish last year.
去年，她和一个叫麦克塔维什的男人私奔了。
2、They were knocking around together for about a year.
他们交往大概有一年了。
3、Douglas was a 29-year-old journeyman fighter, erratic in his previous fights.
道格拉斯29岁，是个技术不错的拳击手，在以前的比赛中发挥不太稳定。
