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

Example Input: Sentence1: Antibodies are large, Y-shaped proteins that recognize and bind to antigens. 
Sentence2: Some of the antibodies, antophospholipid antibodies, cause blood clots.
Example Output: Antibodies

Example Input: Sentence1: Beavers are primarily aquatic animals. 
Sentence2: Beavers require great amounts of water to survive.
Example Output:
Beavers