Feeling sick to the stomach or feeling like you might vomit; also describes something that causes this feeling.
From Latin 'nausea' meaning seasickness, from Greek 'naus' meaning 'ship.' The word literally references the feeling sailors got on boats. It evolved to mean any stomach-based sickness regardless of cause.
Here's a grammar drama: language experts say 'nauseous' technically means 'causing nausea' while 'nauseated' means 'feeling nausea,' but most English speakers have merged them. This happens when the original distinction gets too subtle—people choose the more common word. In 100 years, dictionaries might admit 'nauseous' for both uses since language follows what people actually do.
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