[determiner], [pronoun], [adjective], [adverb] [not gradable], nounMy grandmother's celebrating her sixtieth birthday on Sunday."How many exam papers have you marked now?" "This is the sixtieth."They were/came finished sixtieth out of a hundred.A sixtieth is one of sixty equal parts of something.
SIXTIETH
Meaning of SIXTIETH in English
Cambridge English vocab. Кембриджский английский словарь. 2012