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: Viruses contain DNA but not much else. 
Sentence2: viruses contain encoded information but not much else.
Example Output: Viruses

Example Input: Sentence1: Genetics is the study of inheritance. 
Sentence2: Pedigrees are useful tools for studying genetics.
Example Output: Genetics

Example Input: Sentence1: fog is formed by water vapor condensing in the air. 
Sentence2: An example of water vapor is steam.
Example Output:
vapor