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: Proper digestion is vital for nutrient absorption. 
Sentence2: Digestion is important for an animal's survival.
Example Output: digestion

Example Input: Sentence1: Bacteria and Viruses Bacteria and viruses can cause diseases. 
Sentence2: bacteria can have a negative impact on an organism.
Example Output: Bacteria

Example Input: Sentence1: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: Fault zones are plates in the earth that slide and collide.
Example Output:
faulting