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: Conventional myosin is required for cytokinesis . 
Sentence2: Conventional myosin is required for the final stage of cell division.
Example Output: Conventional

Example Input: Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain. 
Sentence2: Plants can reduce fatigue during the daytime.
Example Output: fatigue

Example Input: Sentence1: Lions hunt in prides, the killing is usually done by the swifter young lions. 
Sentence2: lions are social groups that hunt.
Example Output:
Lions