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: Information on DNA is organized into genes. 
Sentence2: DNA codes for proteins.
Example Output: DNA

Example Input: Sentence1: Algae have varied life cycles. 
Sentence2: And fish eat algae.
Example Output: Algae

Example Input: Sentence1: Pencil lead is a mixture of graphite and clay. 
Sentence2: clay is used to make pencils.
Example Output:
clay