nineties是什么意思

Ninety is the number 90.

When you talk about the nineties, you are referring to numbers between 90 and 99. For example, if you are in your nineties, you are aged between 90 and 99. If the temperature is in the nineties, the temperature is between 90 and 99 degrees.

The nineties is the decade between 1990 and 1999.