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: if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity. 
Sentence2: Most seeds are more dense than water.
Example Output: dense

Example Input: Sentence1: Metabolic rate is the rate at which food is burned for energy. 
Sentence2: thyroid hormones increase the rate of energy consumption.
Example Output: energy

Example Input: Sentence1: Snakes are cold-blooded reptiles. 
Sentence2: snakes produce amniotic eggs.
Example Output:
Snakes