Zastosowanie „unless”

Unless oznacza to samo co if...not. Podobnie jak w przypadku if, po unless następuje czas teraźniejszy, przeszły prosty lub przeszły Past Perfect (nigdy tryb przypuszczający). Unless stosujemy zamiast if...not w okresach warunkowych wszystkich typów. Kolejność zdań składowych nie ma znaczenia w zdaniach zawierających unless.

I okres warunkowy: unless + czas teraźniejszy
Z if Odpowiednik z 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.
II okres warunkowy: unless + czas przeszły
Z if Odpowiednik z 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.
III okres warunkowy: unless + czas Past Perfect
Z if Odpowiednik z 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.