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: Digestion is the process of breaking down food into components the body can absorb. 
Sentence2: Saliva starts to break down the food.
Example Output: breaking

Example Input: Sentence1: Viruses are not affected by antibiotics. 
Sentence2: Viruses are not affected by medicine that helps prevent infection.
Example Output:
Viruses