Questions & Answers about Nescio quid in foro fieri possit.
- Nescio: I do not know; 1st person singular present active indicative of nescire
- quid: what; neuter singular interrogative pronoun
- in: in
- foro: in the forum / marketplace; ablative singular of forum
- fieri: present passive infinitive of facere; here it can mean to be done or idiomatically to happen
- possit: may be able / can / may; 3rd person singular present subjunctive of posse
So the basic structure is I do not know + what + can happen / be done + in the forum.
Because quid in foro fieri possit is an indirect question after nescio.
Latin regularly uses the subjunctive in indirect questions:
- Scio quid faciat = I know what he is doing
- Rogo ubi sit = I ask where he is
- Nescio quid possit = I do not know what can happen
So possit is not subjunctive because the action is unreal; it is subjunctive because the clause is grammatically an embedded question.