IPA: //ˈfɪf.tiːn//
KK: /ˈfɪfˌtin/
The number that comes after fourteen and before sixteen, often used to count or indicate a quantity.
There are fifteen students in the classroom.
Fifteen → The word 'fifteen' originates from Old English 'fīftene', which is a combination of 'fīf' (meaning five) and 'tīene' (meaning ten). Thus, fifteen literally means five plus ten.
Think of 'five' and 'ten' coming together to make 'fifteen' — that's how you can remember that fifteen is the number that follows fourteen.
No commonly confused words.