In relation to any two loci, the occurrence of haplotypes (gametes) with a frequency equal to the product of the frequency of the two relevant alleles, e.g., loci A and B are in linkage equilibrium if the frequency of the haplotype (gamete) A_iB_i equals the product of the frequencies of alleles A_i and B_i. a.k.a. linkage equilibrium, but this is a misleading term, because the concept applies equally to linked and unlinked loci.