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: Consider Input: Sentence1: If there is enough moisture in the clouds, rain is produced. 
Sentence2: Clouds lacking water reduces rainfall.

Output: clouds


Input: Consider Input: Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Dropping an object into lake causes vibrations.

Output: dropping


Input: Consider Input: Sentence1: Size is a relative aggregate measure of volume and mass. 
Sentence2: The volume of an object can be used to measure the mass of the object.


Output: mass