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.

Q: Sentence1: wind is used for producing electricity. 
Sentence2: Winds are caused by pressure differences.

A: wind
****
Q: Sentence1: Leeches are external parasites. 
Sentence2: Leeches live on the surface of their hosts.

A: Leeches
****
Q: Sentence1: heating salt water causes the water to evaporate while the salt remains. 
Sentence2: Evaporation of the water leaves the salt on the surface.

A:
evaporate
****