In normal space, the interior angles of a square measure 90 degrees each. Also, in a right triangle, the angle opposing the hypotenuse measures 90 degrees, with the other two angles adding up to 90 for a total of 180 degrees.

*See also:* eighty, ninety, one hundred, integer, list of numbers.

**Ninety** is also:

- The atomic number of thorium, an actinide.
- The designation of American Interstate 90, a freeway that runs from Washington to Massachusetts.
- The code for international direct dial phone calls to Turkey.
- This article is about the number. For the year AD 90, see 90.