Uso di "unless"

Unless ha lo stesso significato di if...not. Come if, unless è seguito da una voce verbale al presente o al passato o al perfetto (mai da un condizionale). Unless può essere usato al posto di if...not in qualsiasi tipo di periodo ipotetico. L'ordine delle proposizioni è irrilevante quando si usa unless.

Periodo ipotetico 1: Unless + presente
Con if Equivalente con 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.
Periodo ipotetico 2: unless + passato
Con if Equivalente con 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.
Periodo ipotetico 3: unless + past perfect
Con if Equivalente con 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.