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: All life relies on a relatively narrow range of pH, or acidity. 
Sentence2: humans rely on a relatively narrow range of acidity.

Output: acidity


Input: Consider Input: Sentence1: Acids dissolve in base and turn blue litmus red. 
Sentence2: acid changes color.

Output: Acids


Input: Consider Input: Sentence1: bacteria cause food to spoil. 
Sentence2: If food smells or looks spoiled, always throw it out.


Output: spoil