Definition: 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: Sentence1: Muscles are present in opposing groups, as illustrated by the biceps and triceps of the upper arm. 
Sentence2: upper arm muscles contracting causes a person 's elbow to straighten.

upper