I. | ̷ ̷ ̷ ̷| ̷ ̷ adjective
: being one more than eighty in number
eighty-one years
— see number table
II. pronoun, plural in construction
: 81 countable persons or things not specified but under consideration and being enumerated
eighty-one are here
eighty-one were found
III. noun
1. : one and 80 : three times 27 : nine nines : the square of nine
2.
a. : 81 units or objects
a total of eighty-one
b. : a group or set of 81
3. : the numerable quantity symbolized by the arabic numerals 81
4. : the 81st in a set or series