Substitutable and Complementary

adjective

• Of words. ( interchangeable in a given context without changing the import of the expression)
• Capable of being exchanged for another or for something else that is equivalent.
  • synonyms: commutable

• (a.) Serving to fill out or to complete; as, complementary numbers.
• (n.) One skilled in compliments.

noun

• Either one of two chromatic colors that when mixed together give white (in the case of lights) or grey (in the case of pigments. )
  • usage: "yellow and blue are complementaries"
  • synonyms: complementary color

adjective

• Of words or propositions so related that each is the negation of the other.
  • usage: "`male' and `female' are complementary terms"
• Acting as or providing a complement (something that completes the whole. ).
  • synonyms: complemental, completing