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: Butterflies bask to heat up their wing muscles for flight. 
Sentence2: butterflies' instruments of flight are part of the exoskeleton and attached to the thorax.

flight