The os lunatum is a bone located in the wrist that is also known as the moon bone. It is one of the eight small bones that make up the carpal bones in the wrist. Some synonyms for os lunatum include the lunate bone, semilunar bone, crescent moon bone, and moon-shaped bone. The bone is shaped like a half-moon and is key in allowing the wrist to bend and rotate. It serves as a connecting point between the radius bone and other carpal bones. Understanding the various synonyms for os lunatum can help medical professionals and patients alike communicate more effectively about wrist anatomy.