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.

Example Input: Sentence1: Leeches are external parasites. 
Sentence2: Leeches live on the surface of their hosts.
Example Output: Leeches

Example Input: Sentence1: the emission of sulfur dioxide causes acid rain. 
Sentence2: the emission of sulfur dioxide causes soil weathering.
Example Output: causes

Example Input: Sentence1: Weather refers to the conditions of the atmosphere from day to day. 
Sentence2: Rain is a different type of weather.
Example Output:
Weather