"Unless"の使い方

Unless は if...notと同じです。 ifのように、unless の後には現在形、過去形、過去完了形(決して条件付きではありません)。 Unlessは、すべての条件文でif...notの代わりに用いられます。unlessを使った文節の順序に決まりはありません。

Ifを用いて	Unlessを用いた言い換え
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.

Ifを用いて	Unlessを用いた言い換え
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.

Ifを用いて	Unlessを用いた言い換え
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.