What is the difference between pyrexia and fever and temp elevation?

Same/same/different: "pyrexia" and "fever" are 2 words for the same thing. In the U.S. We tend to say "fever, " while "pyrexia" is often used in the U.K. And in places where medical terminology is influenced by british usage. "temperature elevation" is less specific. You can have an elevated temperature that doesn't meet the criteria for fever.