|Origin:||fiftene, from fif 'five' + tien 'ten'|
the number 15:
a coastal village fifteen miles south of Tourane
They met when she was fifteen (=15 years old).
a team of 15 players in Rugby Union
—fifteenth adjective, pronoun:
in the fifteenth century
her fifteenth birthday
I'm planning to leave on the fifteenth (=the 15th day of the month).