1. The ordinal number matching the number 12 in a series.
2. One of 12 equal parts.
[Middle English twelfthe, alteration of Old English twelfta; see dwo- in the Appendix of Indo-European roots.]
twelfth adv. & adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.