四年用英语怎么说

4年是复数，要加s.例如：He has been here for 4 years.但是如果用4-year， 不用加s.例如：She had got a 4-year contract.

english for four years

复数应该是4years

once in four years 或者 every four years 都可以所以是：hold once in four years hold every four years

要加s 如果不想加s可以写4-year

for four years

四年一次每四年一次 once every four years ; Every four year；once four yearsquadrennial英 [kwɒ'drenɪəl] 美 [kwɑd'rɛnɪəl] 跟读 口语练习adj. 每四年一次的；连续四年的n. 第四周年纪念