Divergence is the evolutionary process by which populations become genetically different over time.
Separated populations accumulate differences through mutation, natural selection, genetic drift, and changes in gene flow. The longer populations remain isolated, the more opportunities they have to follow different evolutionary paths.
Divergence can occur before populations become separate species. If genetic differences eventually produce reproductive isolation, the populations may undergo speciation. Divergence can also occur between species that retain some ability to interbreed.
The term is often confused with convergence. Divergence describes related lineages becoming more different, whereas convergence describes unrelated lineages independently evolving similar traits. Divergent evolution can produce homologous structures, such as the forelimbs of humans, bats, and whales, even when those structures now perform very different functions.