在他20岁的时候 用英语有几种表达方式?

when he was 20when he was 20 years oldwhen he was 20-year-oldwhen he was at the age of 20when he turned 20 （特指刚到20岁）when he reached his 20s （也指刚到20岁）in his twentieth 不是指20岁,而是指20-29岁之间。