ninety · number /ˈnɑɪnt.i/
A2 the number 90
eighty, ninety, a hundred
Ninety percent of the people surveyed were in favor.
Friday is the art class day. It is [in] ninety minutes. (Key English Test; A2; Turkish)
(be) in your nineties/90s
B2 to be aged between 90 and 99
He is in his nineties now.
B2 the years 1990 through 1999
I spent most of the nineties traveling around the world.
Another aspect which shows us the danger that the car represents to human life in the nineties [is] pollution. (First Certificate in English; B2; Portuguese)