An autosome is a non-sex chromosome. It is an ordinarily paired type of chromosome that is the same in both sexes of a species. For example, in humans, there are 22 pairs of autosomes. The X and Y chromosomes are not autosomal. Non-autosomal chromosomes are usually referred to as sex chromosomes, allosomes or heterosomes.
^ In the case of higher ploidy levels than the usual diploid, there will be the same number of an autosome as the ploidy level itself. For example, in a pentaploid, there will be five copies of each autosome.