Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: Evaporation of sweat uses energy, and the energy comes from body heat. 
Sentence2: Evaporation of sweat uses energy, and the energy comes from exercise.
Evaporation

Sentence1: Similarly, stars are referred to as suns, but our star is the Sun. 
Sentence2: our star causes water to evaporate more quickly by adding heat.
our

Sentence1: Basically, heat is energy. 
Sentence2: Head hair is especially important in preventing energy loss from the body.

energy