Undescended testis, also known as cryptorchidism, is a congenital condition where one or both testicles fail to descend into the scrotum. There are several synonyms that can be used to refer to this condition, including abdominal testis, ectopic testis, maldescended testis, and retractile testis. Abdominal testis refers to the undescended testicle being located in the abdomen, while ectopic testis means that it is located in an abnormal position. Maldescended testis is a general term that describes any testicle that has not fully descended, while retractile testis refers to a testicle that moves back and forth between the scrotum and abdomen. Early treatment is important as undescended testis can lead to fertility issues and testicular cancer later in life.