Meaning of complementary base

com'plemen'tary base'

Pronunciation: [key]
— Genetics. Genetics.
  1. either of the nucleotide bases linked by a hydrogen bond on opposite strands of DNA or double-stranded RNA: guanine is the complementary base of cytosine, and adenine is the complementary base of thymine in DNA and of uracil in RNA. Cf. base pair.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.