younger than 26,younger than 26 yrs old,younger than 26 years,younger than 26 yrs都是对的吗?

问题描述:

younger than 26,younger than 26 yrs old,younger than 26 years,younger than 26 yrs都是对的吗?
在书面语中,YRS可用吗?

正式的书面语中绝对不行.
非正式的可以,比如说网络聊天、给同学穿个小纸条时就行.
类似YRS的缩略语还有比如plz(please),BTW(by the way)等等.