While comparing and contrasting various aspects of English and German one thing I come across is this: "No" indicates denying or refusing something, thus:
"Is John here?"
But "no" is also used in this sense:
He has no money left.
In German, the first "no" above is "nein", and the second is "kein".
However, "kein" in German is used distinctly more frequently than "no" in that sense is used in English. In particular, a German whose English is fairly good wrote "Spiders are no insects." where I would have written "Spiders are not insects." And his usage seems to match the sort of context in which I would expect "kein" to be used in German.
My question is how to explain to someone like that when to use "no" in the second sense above, and when to use "not" or some other locution.