岁
suì
Age with "sui"
Age needs no verb — the number and 岁 are the predicate.
Subj. + Number + 岁
How it works
我二十岁 means "I'm twenty". There is no 是 and no 有: the measure word 岁 carries the sentence on its own.
Asking depends on who you're asking. 你几岁? is for small children; 你多大? is the normal adult question; 您多大年纪? is polite for older people.
Examples
wǒ èr shí suì
我二十岁。
I'm twenty.
tā ér zi sān suì
他儿子三岁。
His son is three.
nǐ duō dà?
你多大？
How old are you?
Common mistakes
- 我是二十岁 is wrong — drop the 是.