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: freezing means changing from a liquid into a solid by reducing heat energy. 
Sentence2: Water freezes into ice when cooled.
Example Output: freezing

Example Input: Sentence1: a magnet moving in a coil of copper wire can cause an electric current. 
Sentence2: An electric current forms when a magnet is run through an induction coil.
Example Output: current

Example Input: Sentence1: Animals able to lay shelled eggs are called amniotes . 
Sentence2: Reptiles are called amniotes.
Example Output:
amniotes