Nausea refers to the imminent desire to vomit and often precedes or accompanies vomiting. Vomiting refers to the forceful expulsion of gastric contents through the mouth. Retching refers to labored rhythmic respiratory activity that precedes emesis. Regurgitation refers to the gentle expulsion of gastric contents in the absence of nausea and abdominal diaphragmatic muscular contraction. Rumination refers to the regurgitation, rechewing, and reswallowing of food from the stomach.