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: Amphibians are the first true tetrapods, or vertebrates with four limbs. 
Sentence2: Frogs are classified as amphibians.
Example Output: Amphibians

Example Input: Sentence1: decomposition increases the amount of nutrients in the soil. 
Sentence2: decomposition increases the amount of cations.
Example Output: amount

Example Input: Sentence1: Arthropods have a life cycle with sexual reproduction. 
Sentence2: Arthropods have a life cycle with mixing genes up.
Example Output:
Arthropods