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: Sexual union is for pleasure and closeness and for procreation. 
Sentence2: Sperm are deposited in the vagina during procreation.

procreation