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: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.
Example Output: plant

Example Input: Sentence1: Genetics is the study of inheritance. 
Sentence2: Pedigrees are useful tools for studying genetics.
Example Output: Genetics

Example Input: Sentence1: An infection is an invasion of the body by bacteria. 
Sentence2: Scraping oneself on a contaminated object may cause an invasion of the body by bacteria.
Example Output:
bacteria