instruction:
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.
question:
Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.
answer:
bear


question:
Sentence1: a warm front causes cloudy and rainy weather. 
Sentence2: Stratus clouds are associated with a warm front.
answer:
front


question:
Sentence1: Wind is a renewable energy source. 
Sentence2: Using wind to generate power reduces greenhouse gases.
answer:

Wind