Nausea is a feeling of discomfort or queasiness in the stomach that often precedes vomiting. It is a common symptom that can be caused by various factors, such as motion sickness, food poisoning, medication side effects, anxiety, pregnancy, or certain medical conditions. Nausea can be accompanied by other symptoms, such as sweating, dizziness, or abdominal pain, and can be temporary or chronic depending on the underlying cause.