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.
Q: Sentence1: Oceans are one of the largest ecosystems in the world. 
Sentence2: energy enters the ocean in the form of sunlight or chemical compounds.
A: 
Oceans