“Nauseous” is an adjective that means causing nausea or disgust. For example:
- The smell of the rotten food was nauseous.
- The sight of the injury made me feel nauseous.
“Nauseated” is an adjective that means feeling sick to the stomach or experiencing nausea. For example:
- I feel nauseated after eating too much.
- The motion of the boat made me feel nauseated.
In general, “nauseous” refers to something that causes nausea, while “nauseated” refers to the feeling of being sick to the stomach.