The rectum is the last stretch of your large bowel, the part that holds waste until you go to the toilet. After the rectum comes the anus, the opening itself; doctors keep those two names apart, though everyday talk often just says “bottom.” Rectum is a medical word, used in hospitals, biology class, and on medicine notes. It is not a swear word and not a joke word, though people sometimes giggle because the topic is private. The Latin name was rectum intestinum, “the straight intestine,” because that last section runs fairly straight; later it was shortened to rectum. Animals have a rectum too. The adjective is rectal.