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: Contact with infected blood, contaminated needles. 
Sentence2: scraping oneself on an infected needle may cause infection.
Example Output: infected

Example Input: Sentence1: cell division often causes growth. 
Sentence2: Mitosis is cell division.
Example Output: cell

Example Input: Sentence1: if a neutral atom loses an electron then an atom with a negative charge will be formed. 
Sentence2: if a neutral atom loses an electron it will become attracted to positive charges.
Example Output:
atom