Vomiting (also known as puking, throwing up, barfing, emesis, among other names) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be caused by many conditions; it may be present as a specific response to ailments like gastritis or poisoning, or as a non-specific sequela ranging from brain tumors and elevated intracranial pressure to overexposure to ionizing radiation. The feeling that one is about to vomit is called nausea; it often precedes, but does not always lead to vomiting. Antiemetics are sometimes necessary to suppress nausea and vomiting. In severe cases, where dehydration develops, intravenous fluid may be required. Self-induced vomiting can be a component of an eating disorder such as bulimia, and is itself now classified as an eating disorder on its own, purging disorder.
Vomiting is different from regurgitation, though the terms are often used interchangeably. Regurgitation is the return of undigested food back up the esophagus to the mouth, without the force and displeasure associated with vomiting. The causes of vomiting and regurgitation are generally different.