base pair

Definition of base pair
National Cancer Institute

base pair

(bays payr)
Molecules called nucleotides, on opposite strands of the DNA double helix, that form chemical bonds with one another. These chemical bonds act like rungs in a ladder and help hold the two strands of DNA together. There are four nucleotides, or bases, in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). These bases form specific pairs (A with T, and G with C).

Source: NCI Dictionary of Cancer Terms