refers to any chromosome that is not a sex chromosome in humans. Humans have 44 autosomes (arranged in 22 homologous pairs) in the nucleus of each body cell. Irregular numbers may occur through the loss or addition of one or more autosomes, for example, in the case of Down Syndrome. If a homologous pair of autosomes has an extra chromosome, meaning 3 instead of 2) the condition is called trisomy. Conversely, if one member of a homologous pair is absent, the condition is called monosomy.
AUTOSOME: "An autosome is any human chromosome that is not a sex chromosome."