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: Some viruses have an envelope of phospholipids and proteins. 
Sentence2: Some viruses are also enclosed by phospholipids fat and molecules.

viruses