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: Gene flow occurs when individuals move into or out of a population. 
Sentence2: Geographic subdivision decreases how fast individuals move into or out of a population.

population