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: keeping food cold is used for keeping food fresh. 
Sentence2: Keeping food cold is used to keep food simple and natural as possible.
Example Output: cold

Example Input: Sentence1: natural magnetism is used for pointing north by a compass. 
Sentence2: For the ordinary compass, align to the North direction.
Example Output: north

Example Input: Sentence1: Endospores are commonly found in soil and water. 
Sentence2: Endospores are a means of reproduction.
Example Output:
Endospores