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.

Ex Input:
Sentence1: measuring the hardness of minerals requires scratching those materials. 
Sentence2: To figure out the hardness of a mineral, the Moh's scale of hardness is used.

Ex Output:
minerals


Ex Input:
Sentence1: Methane gas is a produced by rotting compost, trash, and human waste. 
Sentence2: Methane gas can be produced by Slime molds.

Ex Output:
Methane


Ex Input:
Sentence1: extreme heat and pressure change rock into metamorphic rock. 
Sentence2: extreme heat and pressure changes rock into marble.

Ex Output:

change