\Thir"ti*eth\, a. [From {Thirty}: cf. AS.
[thorn]r[=i]tig[=o][eth]a.]
1. Next in order after the twenty-ninth; the tenth after the
   twentieth; -- the ordinal of thirty; as, the thirtieth day
   of the month.
2. Constituting or being one of thirty equal parts into which
   anything is divided.

\Thir"ti*eth\, n.
The quotient of a unit divided by thirty; one of thirty equal
parts.