Translation:I will write it on every wall until they have understood.
Non can be used with future events in a way that does not translate to English. (Non appena is another example) With finché the meaning actually changes slightly if non follows:
- Non possiamo entrare finché non abbiamo la chiave/We cannot enter until we have the key
- Finché lui ha la chiave non possiamo entrare/As long as he has the key we cannot enter
A possible translation of "finché" which might make more sense to English speakers when used in the "finché non" form is something I thought up: "as long as"
"We cannot enter as long as we do not have the keys"
Obviously, this does not work where "finché* is by itself, when it simply means "until".
In fact, "finché" always means "as long as", regardless if it is by itself or not. However, in the case of "finche non", its literal translation to English ("as long as not") is not idiomatic and it is better to translate it as "until" instead. Example:
- Puoi dormire finché vuoi.
- Translation: You can sleep as long as you want.
- Ali ha abitato coi suoi zii finché non ha compiuto diciott'anni.
- Literal translation: Ali lived with his aunt and uncle as long as he didn't complete eighteen.
- Idiomatic translation: Ali lived with his aunt and uncle until he was eighteen.