I. ˈād.]ēə̇th, ˈāt], ]iə̇th\ adjective
Etymology: Middle English eightetithe, eightithe, adjective & noun, from Old English hund eahtatigotha, from hund eahtatig eighty + -otha -tha -th — more at eighty
1. : being number 80 in a countable series
the eightieth day
— see number table
2. : being one of 80 equal parts into which something is divisible
an eightieth share of the money
II. noun
( -s )
Etymology: Middle English eightetithe, eīghtithe
1. : number 80 in a countable series
2. : the quotient of a unit divided by 80 : one of 80 equal parts of something
one eightieth of the total