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: drought is when amount of precipitation decreases. 
Sentence2: Drought decreases the availability and abundance of the natural food supply.
Example Output: drought

Example Input: Sentence1: Aggression is behavior that is intended to cause harm or pain. 
Sentence2: Verbal violence is behavior that is intended to cause harm or pain.
Example Output: behavior

Example Input: Sentence1: Energy-saving light bulbs are essentially fluorescent light bulbs. 
Sentence2: Energy-saving is important when electrical energy is used to produce light.
Example Output:
Energy-saving