Fatigue is a condition that is a combined feeling of being sleepy and weary, or drained of energy. It can range from acute to chronic. For some people, fatigue can be a long-term occurrence that affects their ability to carry out daily activities.
Nausea occurs when your stomach feels uneasy or queasy. You may not actually vomit, but you may feel as though you could. Like fatigue, nausea can stem from physical or mental causes.