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: Fully cooking oysters kills the bacteria. 
Sentence2: Fully cooking oysters can prevent illness.
Example Output: Fully

Example Input: Sentence1: Hydrogen bonds cause water to expand when it freezes. 
Sentence2: Hydrogen bonds Hydrogen bonds are primarily electrostatic in origin.
Example Output: Hydrogen

Example Input: Sentence1: H2O is the scientific name for water. 
Sentence2: if soil is permeable then h2o easily flows through the soil.
Example Output:
H2O