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.

Input: Consider Input: Sentence1: the ovaries are used in reproduction. 
Sentence2: Egg released by the ovary.

Output: ovaries


Input: Consider Input: Sentence1: Sound vibrations can be compared to pond ripples. 
Sentence2: dropping an object into water causes pond ripples.

Output: pond


Input: Consider Input: Sentence1: Opossums are a type of mammal called marsupials. 
Sentence2: playing is one way opossums learn how to behave.


Output: Opossums