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: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.
Example Output: Plants

Example Input: Sentence1: Interstellar space contains a plasma. 
Sentence2: interstellar space contains electrons, atoms, and stars.
Example Output: Interstellar

Example Input: Sentence1: Blenders, mixers, lawn mowers convert that same electrical energy into mechanical motion. 
Sentence2: A gasoline lawn mower uses gasoline to get mechanical motion.
Example Output:
mechanical