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: a drought can change the color of an environment from green to brown. 
Sentence2: a lack of water can change the color of an environment from green to brown.

brown