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: Endospores are commonly found in soil and water. 
Sentence2: Dirt is really misplaced soil.
Example Output: soil

Example 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.
Example Output: harming

Example Input: Sentence1: Some arthropods have special excretory structures. 
Sentence2: Arthropods contain jointed appendages.
Example Output:
arthropods