how old; what age
Used to ask someone's age. Polite when combined with ですか or おいくつですか, but 何歳 can be direct; use おいくつ for extra politeness.
How old are you?
How old is your child?
How old has this child turned?
From what age can you drive a car?
何年 asks about a number of years (duration) or a calendar year, while 何歳 specifically asks a person's age.
Standard kanji spelling using the formal character for age.
Common simplified spelling using the character for 'talent'; widely used in informal writing.
Compound of 何 (なん, 'what') and 歳 (さい, counter for age). The alternative spelling 何才 uses a common substitute character for 歳.