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: Interest in fossils is worldwide. 
Sentence2: paleontologists study something with worldwide interest.
Example Output: Interest

Example Input: Sentence1: If the skin is painful, seek medical attention. 
Sentence2: If your skin hurts, your touch receptors will sense differences.
Example Output: skin

Example Input: Sentence1: Plants use cellulose for their cell walls. 
Sentence2: Cells walls are fiber.
Example Output:
cell