sev ‧ en ‧ teen /ˌsev ə nˈtiːn◂/ BrE AmE number
[ Language: Old English ; Origin: seofontiene , from seofon 'seven' + tien 'ten' ]
the number 17:
a group of seventeen American military officers
I left home when I was seventeen (=17 years old) .
—seventeenth adjective , pronoun :
in the seventeenth century
her seventeenth birthday
I’m planning to leave on the seventeenth (=the 17th day of the month) .