Learn Farsi: قبل از امتحان، هیچ‌کس در حیاط نمی‌دوید. - Before the exam, nobody was running in the yard.

You simply add the negative prefix ne- right before the mi- prefix. For this verb, it is ne- + mi- + david (the past stem for 'to run'). Because the subject is treated as third-person singular (like he or she), there is no extra personal ending added to the past stem.

Why is the verb negative (نمی‌دوید) when the English translation says nobody was running?

Farsi uses double negatives. Whenever you use a negative word like هیچ‌کس (nobody), the verb in the sentence must also be negative. Literally, this sentence translates to 'nobody was not running.'

Why is there an از after قبل?

In Farsi, when you want to say 'before' followed by a noun, you use the phrase قبل از (ghabl az), which literally means 'before from.' Therefore, 'before the exam' becomes قبل از امتحان (ghabl az emtehân).

Is هیچ‌کس (nobody) treated as a singular or plural word for the verb ending?

It is singular. In Farsi, هیچ‌کس (hich-kas) is treated as a third-person singular subject (just like 'he' or 'she'). That is why نمی‌دوید (ne-mi-david) does not have a personal ending added to the past stem.