eigh ‧ teen /ˌeɪˈtiːn◂/ BrE AmE number
[ Language: Old English ; Origin: eahtatiene , from eahta 'eight' + tien 'ten' ]
the number 18:
At least eighteen bullets were fired.
Jim was eighteen (=18 years old) .
—eighteenth adjective , pronoun :
in the eighteenth century
her eighteenth birthday
I’m planning to leave on the eighteenth (=the 18th day of the month) .