if 的替代與倒裝

🎯 這一課你會學會

用比 if 更精準的方式講條件——unless / as long as / provided that / in case,以及正式的倒裝條件句(Had I known… = If I had known…)。這讓你的條件表達更豐富、更道地、更有層次。

💬 先聽一段對話

Mia: Can I borrow your car?（能借我車嗎?)
Jun: Sure, as long as you fill up the tank.（可以,只要你加滿油。)
Mia: Deal. I'll take an umbrella in case it rains.（成交。我帶把傘以防下雨。)
Jun: Good idea. And call me if there's a problem — actually, should you have any trouble, just text.（好主意。有問題打給我——其實,萬一有麻煩,傳訊就好。)

🔑 if 的替代說法

• unless = if not（除非/如果不):You'll be late unless you hurry.（= if you don't hurry)
• as long as / provided (that) / providing (that) = 只要/條件是:You can stay as long as you're quiet.
• in case = 以防、萬一(預防):Take cash in case the card doesn't work.
• even if = 就算:I'll go even if it rains.

🧩 文法點

① unless = if…not(注意別「雙重否定」):

• You'll fail unless you study. = You'll fail if you don't study.
• ❌ unless you don't study(unless 本身已含否定,別再加 not)。

② as long as / provided that = 「條件是…」(語氣比 if 更強調條件):

• I'll help you as long as you help me back.
• You can borrow it, provided (that) you return it tomorrow.（較正式)

③ in case ≠ if(重要區別):

• if = 如果發生就做:Call me if you get lost.（迷路了才打)
• in case = 事先預防(不一定會發生):Take a map in case you get lost.（先帶著,以防萬一)
• in case 後面用現在式(講未來也是):in case it rains(不是 will rain)。

④ 倒裝條件句(正式、書面,拿掉 if + 倒裝):

• Had I known, I would have helped.（= If I had known…)
• Were I you, I'd accept.（= If I were you…)
• Should you need anything, let me know.（= If you should need…——很客氣,常用在服務/商業)
• 作法:拿掉 if,把 had / were / should 移到主詞前。這是正式語氣,口語仍多用 if。

📒 高頻單字

單字	KK 音標	中譯	例句
unless	/ənˈlɛs/	除非	unless you hurry
provided	/prəˈvaɪdɪd/	條件是	provided you agree
in case	/ɪn kes/	以防	in case it rains
otherwise	/ˈʌðɚˌwaɪz/	否則	Hurry, otherwise we'll be late.
suppose	/səˈpoz/	假設	Suppose it rains — then what?

🗣️ 發音提醒

• unless /ənˈlɛs/:重音在後 less。
• provided /prəˈvaɪdɪd/:重音在中間 vai。
• 倒裝句 Had I / Were I / Should you 開頭時,語調帶點正式、平穩。

✍️ 開口練習

練習 1:unless / as long as / in case?

• Take an umbrella ＿ it rains.（預防)→ in case
• You'll miss the bus ＿ you leave now.（如果不)→ unless
• You can play ＿ you finish your homework.（條件)→ as long as

練習 2:改成倒裝(正式)。

• If I had known → Had I known
• If you should need help → Should you need help

練習 3:用 as long as 給一個條件。

You can ＿, as long as ＿.

🎒 帶走

• unless(=if not,別再加 not)、as long as / provided that(條件)、in case(預防,≠ if)。
• 倒裝條件句(Had I known / Were I you / Should you need)= 正式語氣,拿掉 if + 倒裝。

下一課,講過去的習慣與委婉願望:過去的 would、would rather、it's time + 過去式。