Definition of "haplogroup"

A haplogroup comprises the genes present on one chromosome.

1984, Alfred Nisonoff, Introduction to Molecular Immunology, page 128

The earlier Amerind migration carried with it only four Asian haplotypes, which subsequently evolved into Amerind-specific haplogroups A, B, C, and D.

1993, “mtDNA Variation of Aboriginal Siberians Reveals Distinct Genetic Affinities with Native Americans”, in American Journal of Human Genetics, volume 53, page 591