Ninety is a number characterized to be one more than eighty-nine and the result of 9 multiplied by 10. It is presented numerically as 90.
"You have approximately ninety seconds to apologize for that nasty behavior."
Ninty stands to be the most popular incorrect spelling for the number, 90. Just remember to put 'e', and if it is difficult, it would be advisable to represent ninety as 90 to avoid such error.