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: Bivalves feed on plankton and nonliving organic matter. 
Sentence2: Clams feed on plankton and nonliving organic matter.
Example Output: feed

Example Input: Sentence1: an animal requires warmth for survival. 
Sentence2: Light and heat and warmth are basic necessities for survival.
Example Output: warmth

Example Input: Sentence1: eating food that contains pesticides can have a negative impact on humans. 
Sentence2: Pesticides are toxic to both humans and the environment.
Example Output:
humans