thir•ti•ethPronunciation: (thûr'tē-ith), [key]
next after the twenty-ninth; being the ordinal number for 30.
being one of 30 equal parts.
a thirtieth part, esp. of one (1/30
the thirtieth member of a series.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.