"There are no radios outside."
Translation:Kint nincsenek rádiók.
Sure, nincs is singular (it is the negative of van), and nincsenek is plural (the negative of vannak).
Oh, sorry! Nincsen is a synonym of nincs, the singular one. There is no difference in meaning or grammar. The only reason you might choose the longer word is if the sound or rhythm of it seems nice (it's convenient for poets to have an extra syllable sometimes).