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.
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Question: Sentence1: Osteoporosis is a disease in which osteoclasts are more active than osteoblasts. 
Sentence2: a thinning and weakening of bone is a disease in which osteoclasts are more active than osteoblasts.

Answer: active


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

Answer: bear


Question: Sentence1: a cactus stem is used for storing water. 
Sentence2: a cactus stem is used for storing h2o.

Answer:
cactus