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.
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Question: Sentence1: Finally, the fluid in the nephron reaches a collecting duct . 
Sentence2: fluid in the kidneys collect into ducts.

Answer: fluid


Question: Sentence1: harming an animal species has a negative impact on the population size of that species. 
Sentence2: Pesticides have a negative impact on the population size of a species.

Answer: impact


Question: Sentence1: the looseness of soil has a positive impact on a plant 's roots' growth in that soil. 
Sentence2: Tree roots stabilize the soil and prevent soil erosion.

Answer:
soil