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: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.
Example Output: temperature

Example Input: Sentence1: Eggs are usually laid in a nest. 
Sentence2: birds have nests.
Example Output: nest

Example Input: Sentence1: For one, animal fur becomes thicker and more abundant during the winter months. 
Sentence2: In the winter months, animal fur is more abundant for warmth.
Example Output:
abundant