twelfth

I. twelfth /twelfθ/ BrE AmE noun [countable]
[Language: Old English; Origin: twelfta, from twelf; ⇨ ↑twelve]
one of twelve equal parts of something

Oxford Advanced Learner's Dictionary

twelfth

twelfth [twelfth twelfths] [twelfθ] ; [twelfθ] ordinal number, noun There are examples of how to use ordinal numbers at the entry for fifth.

Main entry: twelve_derived

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

twelfth / twelfθ / ordinal number

12th written as a word:

Our next meeting is on the twelfth ( of May).

Collins COBUILD Advanced Learner’s English Dictionary

twelfth

[twe̱lfθ]
♦♦
twelfths
1) ORD The twelfth item in a series is the one that you count as number twelve.
  ...the twelfth anniversary of the April revolution.
  ...a twelfth-century church.
2) FRACTION A twelfth is one of twelve equal parts of something.
  She is entitled to a twelfth of the cash.

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

twelfth

²twelfth adj : occupying the number 12 position in a series
• the twelfth day in a row
• finished in twelfth place
- twelfth adv
• Our son finished twelfth in the race.
• the twelfth best-selling book