eightieth/ˈeɪ.ti.əθ/EtymologyFrom earlier eighteth, from Middle English eightetithe, eiȝtetithe, eiȝtithe; equivalent to eighty + -eth. For the modern form, see the etymological notes at twentieth.eightieth means the ordinal form of the number eighty. Lexicurio rates it Rare gem — a strength score of 79 out of 100.adjThe ordinal form of the number eighty.nounThe person or thing in the eightieth position.One of eighty equal parts of a whole.