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: Opportunistic infections, such as Pneumocystis carinii pneumonia, begin to occur. 
Sentence2: Opportunistic infections may be a result of an infection or injury of the lungs.

Opportunistic