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: clouds are formed by water vapor rising into colder regions of the atmosphere and condensing. 
Sentence2: clouds are formed by h2o vapor rising into colder regions of the atmosphere and condensing.

formed