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: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.
Example Output: temperature

Example Input: Sentence1: the mass of an object causes the gravitational force exerted by that object. 
Sentence2: gravitational force accelerates objects.
Example Output: force

Example Input: Sentence1: Glucose is used for energy by the cells of most organisms. 
Sentence2: sugar is used for energy by the cells of most organisms.
Example Output:
cells