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: Viruses are so small that they can be seen only with an electron microscope. 
Sentence2: Tobacco Mosaic is so small that it can only be seen with an electron microscope.

electron