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: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.
[A]: Cow


[Q]: Sentence1: Rivers, rainwater, well water and most lakes contain fresh water. 
Sentence2: canyons are formed by rainwater.
[A]: rainwater


[Q]: Sentence1: if a neutral atom loses an electron then an atom with a negative charge will be formed. 
Sentence2: When an atom or molecule is no longer neutral it is called an ion .
[A]:
neutral