noun, plural: heterochromosomes
A chromosome that is different from an ordinary autosome in form, size, or behavior; a sex chromosome.
Unlike autosomes that are the same in form, size and behavior in both sexes of a species, heterochromosomes are not. In humans, the X and Y chromosomes are an example of such type of chromosome.
Word origin: from Greek heteros meaning different and Greek sôma meaning body.