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: All lizards are reptiles. 
Sentence2: Lizards are tetrapod vertebrates that produce amniotic eggs.
Example Output: lizards

Example Input: Sentence1: Petals attract pollinators to the flower. 
Sentence2: Something a daisy has attracts pollinators.
Example Output: attract

Example Input: Sentence1: cycles of freezing and thawing water cause ice wedging. 
Sentence2: cycles of freezing and thawing water cause mechanical weathering.
Example Output:
cause