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: Osteoporosis is a disease characterized by a decrease in bone mineral density. 
Sentence2: a disease in which osteoclasts are more active than osteoblasts results in a decrease in bone mineral density.
[A]: bone


[Q]: Sentence1: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.
[A]: bike


[Q]: Sentence1: And slow sperm is one of the leading causes of male infertility . 
Sentence2: slow sperm may not swim fast.
[A]:
slow