... years old; age (of) ...
Counter suffix attached to numbers to express age. 歳 is the standard kanji; 才 is a common informal simplification.
He is ten years old.
He will turn 20 next month.
How old are you? — I'm eight.
Excuse me, but how old are you?
You have the right to vote from the age of 18.
A 5-year-old child is playing in the park.
歳 is the standard counter for age (二十歳), while 才 is sometimes used informally in its place but is properly the word for innate talent or a volume unit.
年齢 is the abstract noun meaning 'age', while 歳 is the counter attached to a number, as in 20歳 (20 years old).
歳 is the counter attached after a number to state someone's age (二十歳), while 年 is the noun that can mean age, a calendar year, or old age on its own.
Standard kanji for age; used in formal and everyday contexts.
Simplified variant often used in informal writing or when the full kanji is considered difficult.
The kanji 歳 originally relates to the harvest cycle and came to mean 'year' and 'age'. The simplified form 才 is a homophonous kanji adopted for convenience.