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: a battery converts chemical energy into electrical energy. 
Sentence2: A battery produces a flow of electrons.
Example Output: battery

Example Input: Sentence1: infection can cause bodily tissues to swell. 
Sentence2: Bacteria can cause bodily tissues to swell.
Example Output: bodily

Example Input: Sentence1: Yeast reproduce asexually by budding. 
Sentence2: some fungi reproduce asexually by budding.
Example Output:
asexually