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: 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: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.
Example Output: moss

Example Input: Sentence1: Mushrooms are also fungi. 
Sentence2: mushrooms lack chlorophyll, so they cannot make food by photosynthesis as plants can.
Example Output:
Mushrooms