Nine (noun)

1. The number equivalent to the product of three and three; one more than eight and one less than ten.
2. A group or unit of nine individuals or things.

Origin:

From old english 'nigon', from proto-germanic 'newun'.

Examples:

1. She turned nine years old last week.
2. The baseball team has nine players on the field at once.
3. The music group consists of nine members.