Wiktionary
n. (context fractional English) One of thirty-one equal parts of a whole. num. (context ordinal English) The ordinal form of the number thirty-one, describing a person or thing in position number 31 of a sequence.
WordNet
adj. coming next after the thirtieth in position [syn: 31st]
Usage examples of "thirty-first".
If the engines are not back on line by the thirty-first, the ship will be too fast to enter Jupiter Roads, which will delay our arrival.
As the Crimean War enters its one hundred and thirty-first year, pressure groups both at home and abroad are pushing for a peaceful end to hostilities.
But I'll tell you this much: the prospect of that prize-giving on the thirty-first of this month has been turning my existence into a nightmare.
Sterling Harper had a round-trip ticket on The Virginian for October twenty-seventh, returning on the thirty-first.
To have the living he was required to subscribe to the Thirty-Nine Articles, and the thirty-first describes Masses - forgive me - as blasphemous fables and dangerous deceits.