thirty-first

adjective

Definition of thirty-first

(Entry 1 of 2)

1 : being number 31 in a countable series the thirty-first day — see Table of Numbers

2 : being one of 31 equal parts into which anything is divisible a thirty-first share of the money

thirty-first

noun

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Definition of thirty-first (Entry 2 of 2)

1 : number 31 in a countable series the thirty-first of the month

2 : the quotient of a unit divided by 31 : one of 31 equal parts of anything one thirty-first of the total