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: a battery converts chemical energy into electrical energy. 
Sentence2: Battery electricity comes conversion.

A: battery
****
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: Aging is associated with the death of cells. 
Sentence2: Telomeres degrade as the cells divide and their shortening causes cell death.

A:
cells
****