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: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.
Example Output: earthquakes

Example Input: Sentence1: Flagella help prokaryotes move. 
Sentence2: flagella help bacteria move.
Example Output:
Flagella