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: a flower 's purpose is to produce seeds. 
Sentence2: Every job has meaning and purpose.
Example Output: purpose

Example Input: Sentence1: an animal requires nutrients to grow and heal. 
Sentence2: Microbes can help an animal to grow and heal.
Example Output: grow

Example Input: Sentence1: Sonar bounces sound waves off the bottom of the ocean. 
Sentence2: Bouncing sound waves off the bottom of the ocean is used to find locations of objects.
Example Output:
bottom