Unless means the same as if...not. Like if, unless is followed by a present tense, a past tense, or a past perfect tense (never by a conditional). Unless is used instead of if...not in conditional sentences of all types. The order of the clauses doesn't matter with sentences using unless.
TYPE 1 CONDITIONAL: UNLESS + PRESENT TENSE
|
With If |
Equivalent with Unless |
|
You will be sick if you don't stop eating. |
You'll be sick unless you stop eating. |
|
I won't pay if you don't provide the goods immediately. |
I won't pay unless you provide the goods immediately. |
|
If you don't study dilligently, you'll never understand trigonometry. |
Unless you study dilligently, you'll never understand trigonometry. |
TYPE 2 CONDITIONAL: UNLESS + PAST TENSE
|
With If |
Equivalent with Unless |
|
If he wasn't very ill, he would be at work. |
Unless he was very ill, he would be at work. |
|
I wouldn't eat that food if I wasn't really hungry. |
I wouldn't eat that food unless I was really hungry. |
|
She would be here by now if she wasn't stuck in traffic. |
She would be here by now unless she was stuck in traffic. |
TYPE 3 CONDITIONAL: UNLESS + PAST PERFECT
|
With If |
Equivalent with Unless |
|
Our director would not have signed the contract if she hadn't had a lawyer present. |
Our director would not have signed the contract unless she had had a lawyer present. |
|
I wouldn't have phoned him if you hadn't suggested it. |
I wouldn't have phoned him unless you'd suggested it. |
|
They would have shot her if she hadn't given them the money. |
They would have shot her unless she'd given them the money. |
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