Source : Webster's Revised Unabridged Dictionary (1913)

Twentieth \Twen"ti*eth\, a. [From {Twenty}; cf. AS. twentigo?a.
   See {Twenty}.]
   1. Next in order after the nineteenth; tenth after the tenth;
      coming after nineteen others; -- the ordinal of twenty.

   2. Consisting, or being, one of twenty equal parts into which
      anything is divided.

Twentieth \Twen"ti*eth\, n.
   1. The next in order after the nineteen; one coming after
      nineteen others.

   2. The quotient of a unit divided by twenty; one of twenty
      equal parts of one whole.

Source : WordNet®

twentieth
     n : position 20 in a countable series of things

twentieth
     adj : coming next after the nineteenth in position [syn: {20th}]