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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
Example Output: bacteria

Example Input: Sentence1: Macroevolution occurs over geologic time above the level of the species. 
Sentence2: adding new genes with special capability occurs over geologic time above the level of the species.
Example Output: above

Example Input: Sentence1: the volume of an object can be used to describe the size of that object. 
Sentence2: Volume means how much space the ingredient takes up.
Example Output:
volume