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: Veins generally carry deoxygenated blood. 
Sentence2: Blood carries blood cells.
Example Output: blood

Example Input: Sentence1: a switch is used to start the flow of current in an electrical circuit. 
Sentence2: The flow of electrical current powers a light bulb.
Example Output: current

Example Input: Sentence1: Algae play significant roles as producers in aquatic ecosystems. 
Sentence2: Algae play significant roles as producers oceans.
Example Output:
Algae