
nounplural:
 Two angles whose sum is 90°.
 Two sides whose amount is 90°.

noun:
 a set of perspectives that sum to the right direction.
 two sides whose sum is a right angle
 A pair of perspectives that sum to a right position.
 two perspectives whose sum is a right position

adjective:
 two sides whoever sum is 90°.
 two angles whoever sum is 90°.
How would you define complementary angles?