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: Running water is better able to dissolve oxygen and nutrients than standing water. 
Sentence2: Oxygen and nutrients dissolve easily in rivers.
Example Output: dissolve

Example Input: Sentence1: If the skin is painful, seek medical attention. 
Sentence2: If your skin hurts, your touch receptors will sense differences.
Example Output: skin

Example Input: Sentence1: extreme heat and pressure change rock into metamorphic rock. 
Sentence2: Extreme heat and pressure can change rock into slate.
Example Output:
change