conjunction
Except if; used to say that something will happen only when a particular condition does not happen.
We won't leave unless the rain stops.
You can't enter unless you have a ticket.
Good to know
Unless often means “if not,” so an extra not can change the meaning. For a future condition, use the present form after unless, not will.
Common phrases & grammar
unless + subject + verb, subject + will + verb
subject + will + verb + unless + subject + verb