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.

Example Input: Sentence1: Hydrogen bonds cause water to expand when it freezes. 
Sentence2: Water freezes into ice when cooled.
Example Output: freezes

Example Input: Sentence1: Most mammals have hair, or fur, covering their body. 
Sentence2: Most mammals have a body covering for keeping warm.
Example Output: body

Example Input: Sentence1: And where there's ozone, there's smog. 
Sentence2: ozone contains particulates.
Example Output:
ozone