The
epididymis (; plural: epididymides or ) is a tube that connects a
testicle to a
vas deferens in the
male reproductive system. It is present in all male reptiles, birds, and mammals. It is a single, narrow, tightly-coiled tube (in adult humans, six to seven meters in length) connecting the
efferent ducts from the rear of each testicle to its vas deferens.