/twelfth/ , adj.
1. next after the eleventh; being the ordinal number for 12.
2. being one of 12 equal parts.
n.
3. a twelfth part, esp. of one ( 1 / 12 ).
4. the twelfth member of a series.
[ bef. 900; ME twelfthe, twelfte, OE twelfta, equiv. to twelf TWELVE + -ta -TH 2 ]