/fif"teenth"/ , adj.
1. next after the fourteenth; being the ordinal number for 15.
2. being one of 15 equal parts.
n.
3. a fifteenth part, esp. of one ( 1 / 15 ).
4. the fifteenth member of a series.
5. Music. the interval of two octaves.
[ bef. 900; ME fiftenthe (see FIFTEEN, -TH 2 ); r. ME fiftethe, OE fifteotha ]