Unless значит то же, что и if...not. Как и в случае с if, после unless идёт настоящее время, прошедшее время или прошедшее совершенное время (но никогда не условное). Unless используется вместо if...not во всех типах условных предложений. В условных предложениях с unless порядок простых предложений не имеет значения.
1-й тип условия: Unless + настоящее время
| Употребление с If | Эквивалент с 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. |
2-й тип условия: Unless + прошедшее время
| Употребление с If | Эквивалент с 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. |
3-й тип условияl: Unless + прошедшее совершенное время
| Употребление с If | Эквивалент с 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. |