nonne

Nonne is non plus the enclitic -ne, and it stands first in its clause. Latin marks what answer a question is fishing for, and this is the trio: nonne expects yes, num expects no, and plain -ne attached to the first word is neutral. Nonne venit means "he came, didn't he?"; num venit means "he didn't come, did he?".

Two things to hold on to. The English translation almost always has to invert into "surely" or "is it not the case that", because a literal "not" reverses the sense. And nonne survives into indirect questions, where it takes the subjunctive: quaesivit nonne venisset. Rhetoric loves it, which is why Cicero and the church fathers use it in strings, piling up questions nobody is expected to answer.