STRUCTURE
結構
As mentioned above, unless is a conjunction which we use in conditional phrases. In written English, the clause that follows unless is the subordinate clause (SC) meaning that it needs a main clause (MC) to make a complete sentence. It is similar to how we use if in conditional phrases.
之前提過，unless是在條件句中使用的連詞。在書面語種，使用unless的從句叫做從屬句(SC)，需要主句(MC)讓句子完整。這就像if在條件句里的用法一樣。
When unless comes before a main clause we use a comma:
unless放在主句之前加逗號：
Unless it rains, we’ll go for a picnic tomorrow.
[en](SC) (MC)
[/en]
除非下雨，否則我們明天去野餐。
When the main clause comes first, no comma is required:
主句在前，不需要逗號：
They won’t come unless you invite them.
[en](MC) (SC)
[/en]
除非你邀請他們，否則他們不會來。
Unless is like If in that we don’t not use will/would after it. We only use the present simple tense.
像if一樣，我們不會在unless后面使用will/would。只使用一般現在時。
Unless I hear from you, I’ll see you at 5pm.
除非你通知我，否則我和你下午5點碰面。
HOW DO WE USE “UNLESS”?
如何使用“unless”?
Unless and if not
unless和if not
Ok, so unless is similar to “if …..not” and together they mean “except if”. Note: We refer to real conditional situations and NOT impossible situations.
unless和if…not很相似，它們都表示“除非”。注意：我們指的是真實的條件情況，而不是不可能的情況。
If you don’t study, you will fail your exam./ Unless you study, you will fail.
如果你不學習，你考試就過不了。/除非你學習，否則你就過不了考試。
We could eat at Frankie and Benny’s if they’re not closed on a Monday/ We could eat at Frankie and Benny’s unless they are closed on a Monday.
如果弗蘭基&班尼餐館周一不關門，我們可以在那吃飯。/除非弗蘭基&班尼餐館周一關門，否則我們就在那吃飯。
I’ll make dinner if nobody wants to/ I’ll make dinner unless someone else wants to.
如果沒人想做飯的話，我做吧。/除非沒別人想做飯，那么我就來做吧。
If you don’t stop smoking, you will feel bad/ Unless you stop smoking, you will feel bad
如果你不戒煙，你會不舒服的。/除非你戒煙，不然你會感覺不舒服。
Note that the sentence after unless is always a positive sentence. You cannot have a negative sentence after unless because that would make the sentence a double negative and senseless.
注意：unless之后的句子總是肯定的。在unless之后不能接否定句，因為這就造成了雙重否定，句子沒有意義。
Example: Unless you don’t study, you will fail. (????)
例句：除非你不學習，否則你就會失敗。(小編注：即使是此句的中文譯文也是一個有語義問題的病句，雙重否定后使句子無邏輯意義了，符合邏輯的句子應該是“除非你學習，否則你就會失敗。”)
***Warning: Typical Error
警告：典型錯誤
We don’t use “unless” when we mean if.
表示“如果”的時候不用unless。
Example: If you feel ill, I can drive/ Unless you feel ill, I can drive
例句：如果你覺得不舒服，我來開車吧。/除非你覺得不舒服，否則我來開車吧。
Spoken English
口語
When speaking, we use unless to introduce an extra thought or piece of information:
說話的時候，我們用unless表達一些額外的思考或者是信息：
He didn’t even know about the crash – unless he’d heard about it on the radio.
他都不知道那場空難—除非他在廣播上聽說了。
A: Oh look. Neil next door’s got a new car.
A：看!尼爾的鄰居有了輛新車!
B: Unless they’ve got a visitor.
B：除非他們來客人了。
HOW ABOUT “NOT UNLESS”?
not unless的用法呢?
Not unless is similar to only if
not unless和only if相似
Example:
例句：
Shall I tell Liz what happened? Not unless she asks you (= only if she asks you)
我需要告訴利茲發生的事嗎?除非她問起來。
Will you come shopping with me? Not unless you offer me lunch (= only if you offer me lunch)
你和我一起去逛街嗎?除非你給我提供午餐。
