1. ninety-first - Noun
2. ninety-first - Adjective
ninety-first
The ordinal form of the number ninety-one, describing a person or thing in position number 91 of a sequence.
The answer appears on the ninety-first page of the book.
She finished ninety-first in the race.
ninety-first (plural ninety-firsts)
One of ninety-one equal parts of a whole.
A ninety-first of 1820 is 20.