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: hiding can be used for avoiding predators. 
Sentence2: Camouflage is used for avoiding predators.
Example Output: avoiding

Example Input: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.
Example Output: bear

Example Input: Sentence1: high pressure systems cause clear weather. 
Sentence2: During windy weather, the pollution is dispersed and cleared away.
Example Output:
clear