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: harming an animal species has a negative impact on the population size of that species. 
Sentence2: the rarity of a species increases harm to population exponentially.

Ex Output:
harming


Ex Input:
Sentence1: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: animals with jaws have a complete digestive system and a closed circulatory system.

Ex Output:
circulatory


Ex Input:
Sentence1: Diaphoresis is a fancy medical term for perspiration or sweating. 
Sentence2: Evaporation of perspiration uses energy and the energy comes from body heat.

Ex Output:

perspiration