When you talk about the eighties, you are referring to numbers between 80 and 89. For example, if you are in your eighties, you are aged between 80 and 89. If the temperature is in the eighties, the temperature is between 80 and 89 degrees.
双语例句
例： He was in his late eighties and had become the country's most respected elder statesman.
那时他年近九十，并且已经成为该国最受尊敬的政界元老。