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: Each starfish arm is lined with tube feet. 
Sentence2: Starfish are an echinoderm with a unique water vascular system.

starfish