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: Although a diamond is the hardest substance known to man, it can be chipped or scratched. 
Sentence2: measuring the hardness of minerals requires chipping those materials.

chipped