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: Heterotrophs get food by eating other living things. 
Sentence2: fish eat other living things.
Example Output: living

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: All ferns are shade plants. 
Sentence2: Ferns have a characteristic life cycle that includes alternation of generations.
Example Output:
ferns