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: Smoking accelerates the aging process. 
Sentence2: smoking accelerates the death of cells.
Example Output: Smoking

Example Input: Sentence1: Absorption of nutrients occurs mainly in the small intestine. 
Sentence2: The small intestine is the main place where food absorption occurs.
Example Output: intestine

Example Input: Sentence1: moss causes chemical weathering. 
Sentence2: Chemical weathering is the chemical disintigration of rocks.
Example Output:
chemical