Die Verwendung von "unless"

Unless bedeutet dasselbe wie if...not. Genau wieauf if, folgt auf unless der Präsens, der Perfekt oder der Plusquamperfekt, nie aber das Konditional. Unless wird also in Konditionalsätzen statt if...not verwendet. Die Satzstellung ist bei Sätzen mit unless variabel.

Konditional I: Unless + Präsens
Mit 'if' Mit '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.
Konditional II: Unless + Vergangenheit
Mit 'if' Mit '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.
Konditional III: Unless + Plusquamperfekt
Mit 'if' Mit '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.