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: Viral pneumonia is usually milder than bacterial pneumonia. 
Sentence2: Viral and bacterial disease can both be caused by injury of the lungs.

bacterial