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.

[Q]: Sentence1: Most water comes from precipitation. 
Sentence2: aquatic animals require precipitation to survive.
[A]: precipitation


[Q]: 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.
[A]: active


[Q]: Sentence1: Graphite for writing pencils is composed of carbon. 
Sentence2: carbon is a component of pencil lead.
[A]:
carbon