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: Habitat destruction is the primary cause of extinction or threat of extinction for all animals. 
Sentence2: building housing developments may cause extinction.
Example Output: extinction

Example Input: Sentence1: Mitosis is cell division. 
Sentence2: Chromosomes are the form of the genetic material of a cell during mitosis.
Example Output: Mitosis

Example Input: Sentence1: Owls eat small prey. 
Sentence2: Owls catch small creatures to eat.
Example Output:
Owls