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: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.
Example Output: Flies

Example Input: Sentence1: Energy is the fuel for chemical reactions which run the various systems of the body. 
Sentence2: running requires fuel for chemical reactions which run the various systems of the body.
Example Output: body

Example Input: Sentence1: Acetate kinase is found in microbes of the bacteria and archaea domains. 
Sentence2: Acetate kinase is found in one of the domains that scientists still know relatively little about.
Example Output:
Acetate