Orthodontics is the skill and the job of helping teeth grow straight when they have not been growing correctly — lining them up, closing gaps, fixing a bite that does not meet well. It is a branch of dentistry. In English the word looks plural, with -s, but we treat it as one field: “Orthodontics is expensive,” not “are.” You hear it at the dentist, in ads for braces, and in school talk when a teenager gets a wire on their teeth. Everyday English often just says braces; orthodontics is the name of the whole practice, including more than the metal you can see.

齒顎矯正、齒列矯正。中國大陸較常說「正畸」。