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: if soil is permeable then water easily flows through that soil. 
Sentence2: if soil is permeable then h2o easily flows through the soil.
Example Output: flows

Example Input: Sentence1: Insulin is a hormone that helps cells absorb sugar from the blood. 
Sentence2: the pancreas produces a hormone that helps cells absorb sugar from the blood.
Example Output: absorb

Example Input: Sentence1: Among monogamous species of birds and mammals, both parents often care for their offspring. 
Sentence2: The period of parental care after birth for manogamous species are handled by both parents.
Example Output:
monogamous