"Children are playing in the courtyard."
Translation:Во дворе играют дети.
Why is "На дворе играют дети" wrong? What's the difference between "во" and "на"?
Your version would be understood by most, and is, probably, how I would say it. But still, На дворе is wrong just because it is. It's just one of many irregularities that happen all the time.
BTW, На - on, В/во - in.
"На дворе is wrong just because it is" Really ? На дворе трава , на траве дрова. Уж осень на дворе... ты сердце не тревожь... Ведь в рыжем сентябре срывает листья дождь...
Come to think of it, would using на make it more like "Children are playing on the courtyard"? as opposed to the more natural "in the courtyard"? At least in English, this is not wrong, but certainly less natural than using "in" (в). Does this mirror the Russian, native speakers??
American English usually uses "in the yard/courtyard" but "on the grass/pavement in the yard". (There are very few courtyards in the US.)
The Russian use of в + prepositional to often mean "inside" makes the idea of playing "in" the courtyard seem odd - the children would in effect be in the earth underneath the grass or pavement, somehow playing actually in the impenetrable and sold ground, which is quite impossible.
The English "in the yard" lends itself to this crazy interpretation - but is not understood to mean that, because it is impossible. Still, I have seen other exercise here where the distinction is made, so that you would not use В because it would mean that impossible thing.