thirteenth
num.num. the number that comes after twelve. You use it to talk about a position in a list or a specific day of the month.
num. the ordinal number corresponding to the cardinal number thirteen. Often functions as an ordinal determiner or a noun referring to one of thirteen equal parts.
Today is the thirteenth of May.
She finished in thirteenth place out of fifty runners in the local marathon.
The thirteenth floor is often omitted from elevator panels in certain cultures due to long-standing superstitions regarding the number's supposed association with misfortune.
Inherited from Middle English thrittenthe, thrittethe, from Old English þrēottēoþa; equivalent to thirteen + -th (ordinal suffix).
Typically precedes the noun it modifies as an ordinal determiner; can also function as a noun when referring to a fraction.
the thirteen day of the monththe thirteenth day of the monthLearners often use the cardinal number 'thirteen' when the ordinal form 'thirteenth' is required for dates or positions.