Keiner vs Niemand
what would the difference of keiner and Niemand be? are they used in different context?
I had the same question, and found this discussion useful: http://german.stackexchange.com/questions/15111/keiner-jeder-vs-niemand-alle
Also note that "keiner" is not gender-neutral: http://germannn.tumblr.com/post/44440397858/niemand-vs-keiner
They are mostly synonymous. "Niemand" is used exclusively for persons.
Here you cannot replace "keiner" with "niemand": "Keiner der Rasenmäher funktionierte."
"Keiner" can also be used in a relative context, whereas "niemand" is used only absolutely: "Keiner der beiden". Here "niemand" would be strange. But I think that even native speaxers would not notice this kind of nuance most of the time.