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: Viruses are parasites of cells. 
Sentence2: Populations of viruses do not grow through division because they are parasites.
Example Output: are

Example Input: Sentence1: if an animal sweats then that animal 's bodily water decreases. 
Sentence2: When an animal regulates their body temperature by releasing water, their bodily water decreases.
Example Output: bodily

Example Input: Sentence1: All pain receptors are free nerve endings. 
Sentence2: free nerve endings are found in the skin.
Example Output:
endings