1) A haplotype is a set of DNA variations, or polymorphisms, that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms (SNPs) found on the same chromosome. Information about haplotypes is being collected by the International HapMap Project and is used to investigate the influence of genes on disease.

2) A group of alleles of different genes (as of the major histocompatibility complex) on a single chromosome that are closely enough linked to be inherited usually as a unit.