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: Tidal energy is one of the oldest forms of energy used by humans. 
Sentence2: One of the oldest forms of energy used by humans can be used to produce electricity.

forms