A para-functional habit or parafunctional habit is the habitual exercise of a body part in a way that is other than the most common use of that body part. The term is most commonly used by dentists, orthodontists, or maxillofacial specialists to refer to para-functional uses of the mouth, tongue and jaw. Oral para-functional habits may include bruxism (tooth-clenching and/or grinding), tongue tension ("tongue thrusting"), fingernail biting, pencil or pen chewing, mouth breathing, and any other habitual use of the mouth unrelated to eating, drinking, or speaking.