Dipygus is a medical term that refers to a rare congenital condition in which a person is born with two complete legs fused together. While there are no synonyms for the term dipygus, synonyms for similar medical conditions or anomalies include conjoined twins, parapagus, and cephalothoracopagus. These conditions, although different from dipygus, also involve the fusion of body parts. Other terms related to dipygus include polydactyly, which refers to the presence of extra digits, and phocomelia, which refers to the underdevelopment or absence of limbs. The use of medically accurate terminology is important in accurately describing and diagnosing medical conditions.