Haplotype

A haplotype is a term in genetics. It is short for haploid genotype. A haplotype is a collection of specific alleles (particular DNA sequences) in a cluster of tightly-linked genes on a chromosome. A cluster is usually inherited together. Put simply, haplotype is a closely-knit group of genes which a child inherits from one parent.
A second meaning of the term haplotype is a set of single-nucleotide polymorphisms (SNPs) usually found together on a single chromatid (of a chromosome pair). So, finding a few alleles of a haplotype sequence identifies all other sites in its region. Such information is very valuable for investigating the genetics of common diseases.
Comparing haplotypes of two or more people shows the degree of genetic relationship between their respective lines. It is done in genetic genealogy projects.