不变

不變
bùbiàn
  1. constant
  2. unvarying
  3. (math.) invariant

CEDICT

math

Entry Composition

1 不 bù
  1. no; not so
  2. (bound form) not; un-
2 变 biàn
  1. to change
  2. to become different
  3. to transform
  4. to vary
  5. rebellion