The centimorgan (cM) is the unit for measuring genetic linkage by recombination frequency. One centimorgan equals a 1% chance that two allelic markers on the same chromosome will be separated due to recombination in a single generation.

As the recombination frequency between loci related to the physical distance, cM is often used to infer distance along a chromosome. For the human genome, 1 cM approximately equals one million base pairs.