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: harming an animal species has a negative impact on the population size of that species. 
Sentence2: Pesticides have a negative impact on the population size of a species.
[A]: impact


[Q]: Sentence1: Some viruses live in a dormant state inside the body. 
Sentence2: a virus can live in the brain.
[A]: viruses


[Q]: Sentence1: Fractures heal when osteoclasts form new bone. 
Sentence2: New bone is formed by elevated oxygen tensions.
[A]:
bone