Fever (also called pyrexia) is defined as body temperature that is higher than normal for each individual. It generally indicates that there is an abnormal process going on within the body. The severity of a condition is not necessarily reflected by the degree of fever. For example, influenza may cause a fever of 104° F, while pneumonia may cause a very low-grade fever or no fever at all. Consult with your physician if you have any questions about whether a fever is significant.