An autosome is any chromosome other than a sex chromosome. Humans have 23 pairs of chromosomes altogether, 22 of which are pairs of autosomes. Each parent contributes one member to each pair of autosomes.

Homologous chromosomes are two chromosomes of the same type, which are the same size and shape and have the same genes. The paired autosomes are numbered 1 through 22 in order of size, chromosome 1 being the longest and 22 the shortest. A picture called a karyogram is often used to display a set of chromosomes. In a karyogram, homologous chromosomes are placed next to each other. For example, both copies of chromosome 1 are put side by side.