How do you spell Thirtieth

Available Definitions:
1)  a. - Next in order after the twenty-ninth; the tenth after the twentieth; -- the ordinal of thirty; as, the thirtieth day of the month.
2)  a. - Constituting or being one of thirty equal parts into which anything is divided.
3)  n. - The quotient of a unit divided by thirty; one of thirty equal parts.