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: Graphite and diamond are polymorphs of carbon. 
Sentence2: carbon polymorphs are used for making pencil lead.
Example Output: carbon

Example Input: Sentence1: zinc has a positive impact on the healing of wounds. 
Sentence2: oysters have a positive impact on the healing of wounds.
Example Output: has

Example Input: Sentence1: hearing is used for sensing sound by animals. 
Sentence2: functioning ears are used for sensing sound by animals.
Example Output:
animals