How asks for a measure and old describes age. Together they ask for an age.
Age of someone or something
age
neutral
Used to ask or say the age of a person, animal, or thing.
Examples
- How old are you?
- How old is your sister?
- Can you tell how old this tree is?
- She asked how old the dog was.
- How old were you when you learned to swim?
Similar words
what age