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: Most fungi get organic compounds from dead organisms. 
Sentence2: Moulds, yeasts, rusts, smuts, mildews, and mushrooms are all types of fungi.
Example Output: fungi

Example Input: Sentence1: forming coal requires decaying vegetation. 
Sentence2: Forming fossil fuels requires decaying vegetation.
Example Output: decaying

Example Input: Sentence1: Basically, fiber is cellulose . 
Sentence2: Plants are multicelled eukaryotes with cell walls made of fiber.
Example Output:
fiber