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: a fire requires oxygen to burn. 
Sentence2: A fire requires something with exactly eight protons to burn.
Example Output: burn

Example Input: Sentence1: Some herbivores have more than one stomach. 
Sentence2: Camels are an herbivore.
Example Output: herbivores

Example Input: Sentence1: Bone provides protection for soft tissues and internal organs. 
Sentence2: Vertebrae, ribs, appendages, and the jaw are endoskeletal bone.
Example Output:
Bone