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: Herbs are medicines and aids. 
Sentence2: herbs are used for curing people when they are sick.
Example Output: Herbs

Example Input: Sentence1: measuring the hardness of minerals requires scratching those materials. 
Sentence2: To figure out the hardness of a mineral, the Moh's scale of hardness is used.
Example Output: minerals

Example Input: Sentence1: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
Example Output:
bacteria