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: dew is formed when water vapor condenses over night. 
Sentence2: dew is formed when cooling  over night.
Example Output: dew

Example Input: Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.
Example Output: earthquakes

Example Input: Sentence1: Cancer cells divide more often than normal cells, and grow out of control. 
Sentence2: Mutation can cause growth out of control.
Example Output:
control