|Origin:||threotiene, from thrie, threo% 'three' + tien 'ten'|
the number 13:
They've only sold thirteen tickets so far.
When it happened, I was thirteen (=13 years old).
—thirteenth adjective, pronoun:
It's Roberto's thirteenth birthday.
the thirteenth century
I'm planning to leave on the thirteenth (=the 13th day of the month).