The cardinal number occurring after eighty-nine and before ninety-one, represented in Roman numerals as XC and in Arabic numerals as 90. Ordinal: ninetieth
The sum of nine times ten; the number greater by a unit than eighty-nine; ninety units or objects
If the temperature is in the nineties, the temperature is between 90 and 99 degrees. By this time she was in her nineties and needed help more and more frequently