Definition
- B2
Used to indicate what will happen if a specific condition is not met.
否则
We have to get to the airport by five o'clock, or else we'll miss our flight.
我们必须在五点前到机场，否则我们会错过航班。
You had better start writing your report now, or else you won't finish by the deadline.
你最好现在开始写报告，否则你无法在截止日期前完成。
Please turn off the lights when you leave, or else the electricity bill will be high.
请在离开时关灯，否则电费会很高。
- B2
Used to compare two different things or situations, indicating a choice between alternatives.
要不是…就是…
He's either very talkative, or else he's completely silent, there's no in-between.
他要么很健谈，要么完全沉默，没有中间地带。
This restaurant is either packed, or else it's empty; it's hard to predict.
这家餐厅要么人满为患，要么空无一人；很难预测。
This software either works perfectly, or else it crashes completely without warning.
这款软件要么运行完美，要么完全崩溃，没有任何警告。
Used to express a threat, sometimes in a humorous way.
（带威胁意味）要不然，否则
You'd better give me back my money, or else you'll face the consequences!
你最好把我的钱还给我，否则你就会面对后果！
You had better finish your homework now, or else you can forget about playing games!
你最好现在就完成作业，否则就别想玩游戏了！
He had better not cause any more trouble, or else he’ll regret it.
他最好不要再惹麻烦了，否则他会后悔的。