1. (數(shù)字)90
    Ninety is the number 90.

    e.g. It was decided she had to stay another ninety days.
           已經(jīng)決定了，她不得不再呆90天。

2. 九十多;九十幾
    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.

    e.g. By this time she was in her nineties and needed help more and more frequently.
           到這個時候她已經(jīng)90多歲了，越來越頻繁地需要幫助。

3. 九十年代(指1990年至1999年)
    The nineties is the decade between 1990 and 1999.

    e.g. These trends only got worse as we moved into the nineties.
           我們步入20世紀90年代時，這些潮流變得更糟了。