Form
Unless + S + Verb, (Result Clause)
Unless you study, you will fail the test.
I won’t go unless you apologize.
Meanings
Unless = “If… not”
Unless is used to express a negative condition. It means the same as “except if” or “if… not”.
Compare:
Unless you hurry, you will miss the train.
= If you don’t hurry, you will miss the train.