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 flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.
Example Output: flashlight

Example Input: Sentence1: Refraction is the bending of light. 
Sentence2: a rainbow is formed by bending of light by separating light into all different colors.
Example Output: bending

Example Input: Sentence1: Marine biomes are found in the salt water of the ocean. 
Sentence2: Estuaries display characteristics of both marine and freshwater biomes.
Example Output:
Marine