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 are usually considered to be nonliving. 
Sentence2: Viruses are usually acquired from contact with infected animals.
Example Output: Viruses

Example Input: Sentence1: Complex chemistry is needed to carry out all the functions of life. 
Sentence2: Chemistry is primarily concerned with matter, energy, and their interactions.
Example Output: chemistry

Example Input: Sentence1: And leukemia and lymphoma are forms of cancer. 
Sentence2: Leukemia is a disease that occurs when the cell cycle is no longer regulated.
Example Output:
leukemia