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: the Earth being tilted on its rotating axis causes seasons. 
Sentence2: the planet's orbit and tilt causes seasons.
Example Output: seasons

Example Input: Sentence1: cell division often causes growth. 
Sentence2: Mitosis is cell division.
Example Output: cell

Example Input: Sentence1: lack of moisture in the air causes low amounts of rainfall. 
Sentence2: Rainfall contributes to, and evaporation removes, moisture.
Example Output:
moisture