1 [C,U] a condition of the body when it is too hot because of illness 发烧；发热: A high fever can be dangerous, especially in small children.发高烧可以是很危险的，尤其对于小孩子来说。
When somebody's body is very hot we normally say that he/she has a temperature. 说某人发烧，一般用have a temperature。
2 [sing] a fever (of sth) a state of nervous excitement 兴奋；激动