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: the moon revolving around the Earth causes the phases of the moon. 
Sentence2: Lets start our discussion of the Moon's phases with the New Moon phase.
Example Output: phases

Example Input: Sentence1: a fire requires oxygen to burn. 
Sentence2: Oxygen has  eight protons and eight electrons.
Example Output: oxygen

Example Input: Sentence1: Spores may be dispersed by moving water, wind, or other organisms. 
Sentence2: fungi can reproduce with help from moving water, wind, or other organisms.
Example Output:
moving