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: Parasites are organisms that live off a host.
Sentence2: roundworms may be free-living or live off a host.
Example Output: host

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: gases released during the use of fossil fuels causes global warming.
Sentence2: Gases released during the use of fossil fuels threaten the entire planet.
Example Output:
during