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: Mutations that lead to cancer usually occur in genes that control the cell cycle. 
Sentence2: Free radicals that eventually lead to cell death usually occur in genes that control the cell cycle.

usually