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: Birds have a large brain relative to the size of their body. 
Sentence2: Creatures with feathers and wings have a large brain relative to the size of their body.

brain