"One of the cats sleeps."
Translation:En av katterna sover.
It’s one of the cats that sleeps, so it’s singular, therefore sleeps. It’s not all the cats that sleep. I know it’s a slightly awkward sentence in English however.
I don't understand why the word "one" can be en OR ett. I thought one was ett in Swedish. In this sentence it is a particular number called for, not an article.