Differentiate between fever and hyperthermia?

Infections vs heat: Fever is almost aways a sign of an infectious process, most commonly viral--it is a natural defense mechanism to increase chemical process/reaction to help ward off the infection. Hyperthermia is often a result of body generating too much heat (i.E exercising/working too hard)and its failure to evaporate the heat quickly, often because of excessive ambient temperature. I hope this explains it. :-).

Set point difference: Fever is due to an increase in the temperature regulatory set-point. This can be from many things, usually infection, but can be medications, cancer, (the list is large). Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. The set point is the same, the body just can't get the temperature down to the set point. Again many causes, heat stroke most common.