Teacher: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.
Teacher: Now, understand the problem? Solve this instance: Sentence1: the moon revolving around the Earth causes the phases of the moon. 
Sentence2: Phases of the moon, however, depend on the relative positions of the Earth, moon, and Sun.
Student:
Earth