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

Example Input: Sentence1: Producers use energy and inorganic molecules to make food. 
Sentence2: Green plants use energy and inorganic molecules to make food.
Example Output: energy

Example Input: Sentence1: being burried under soil and mud changes vegetation into peat through extreme heat and pressure in a swamp over a long period of time. 
Sentence2: being buried under soil and mud changes vegetation into bogs through extreme pressure and heat.
Example Output:
being