為了強調句子的意思，有時候我們會把句子的結構倒裝；倒裝語序分為全部倒裝和部分倒裝，但是因為倒裝，有時有些句型變得很生疏，甚至是讓人產生錯覺，然而其實只要掌握了一定的識別規則，條件句倒裝結構就是囊中物了。

因為是倒裝，所以句子的開頭不是以助動詞或情態動詞開頭（部分倒裝），就是謂語動詞（實義動詞），其中發生在 if 條件句中的倒裝屬于部分倒裝，此種類型的倒裝主要有以下三種：

一、以 should 開頭的部分倒裝，此時按傳統的歸類，條件句屬于第一類條件句，用來描述你認為將來可能發生的事情，屬于真實條件句，因為雖然我們不知道將來會發生什麼，但是將來還是有可能會發生。

變化規則：should 代替 if，從句中的動詞變成不帶 to 不定式（bare infinitive），如 goes->go，has->have，am/is/are->be，主句不變，例如：

如果你想保持身材，你必須經常鍛煉。

If you want to keep in shape， you must exercise regularly.

Should you want to keep in shape， you must exercise regularly.

如果卡特邀請你參加他的派對，你需要穿上你的新裙子。

If Carter invites you to his party， you need to wear your new dress.

Should Carter invite you to his party， you need to wear your new dress.

二、以 were 開頭的部分倒裝，此時按傳統的歸類，條件句屬于第二類條件句

1、用來表示與將來事實可能相反的事情，變化規則：用 were 代替 if，從句中的動詞變成帶 to 不定式，例如：

如果他按下按鈕，我們都會有問題。

If he pushed the button， we’d all have problems.

Were he to push the button， we‘d all have problems.

如果英國脫歐真的發生，我會感到驚訝。

If Brexit happened， I‘d be surprised.

Were Brexit to happen， I’d be surprised.

2、用來表示現在不可能的事情或情況，因為不是真的，變化規則：去掉 if，主謂對調（I was-> was I），在必要或更準確的語法下用 were I，例如：

如果我真的很富有，我想我還是會工作的。

If I was ridiculously rich， I think I’d still work.

Was I ridiculously rich， I think I‘d still work.

Were I ridiculously rich， I think I‘d still work.

雖然 was 經常出現在對話中，但是在語法上它是不正確的，在英語寫作或考試中要用 were。

三、以 had 開頭的部分倒裝，此時按傳統的歸類，條件句屬于第三類條件句，用來談論過去，描述一個沒有發生的情況，并想象這種情況的結果。

變化規則：去掉 if，主語與 had 對調（we had->had we），主句不變，例如：

如果我們早點到，就不會錯過開頭了。

If we’d arrived sooner， we wouldn’t have missed the beginning.

Had we arrived sooner， we wouldn‘t have missed the beginning.

如果他參加了核酸檢測，他就不會錯過出國的機會。

If he had taken the nucleic acid testing， he wouldn‘t have missed the chance to go abroad.

Had he taken the nucleic acid testing， he wouldn‘t have missed the chance to go abroad.

四、混合條件句中的倒裝，其規則很簡單，就是遵循以上三個原則之一，還是倒從句，主句不變，例如：

如果我有錢的話，我會買我們昨天看到的那輛法拉利。

If I were rich， I would have bought that Ferrari we saw yesterday.

Were I rich， I would have bought that Ferrari we saw yesterday.

如果她上周報名參加滑雪旅行的話，她明天就會加入我們的行列。

If she had signed up for the ski trip last week， she would be joining us tomorrow.

Had she signed up for the ski trip last week， she would be joining us tomorrow.

五、倒裝條件句的否定形式

變化規則：在原有部分倒裝的基礎上，把 not 加在主語后面，例如：

Should Jason attend the wedding， we‘ll be happy.

如果杰森參加婚禮，我們會很高興的。

Should Jason not attend the wedding， we‘ll feel sad.

如果杰森不參加婚禮，我們會難過的。

Were Nelson a smart person， he’d invest all his money in real estate.

如果納爾遜是個聰明人，他會把所有的錢都投資于房地產。

Were Nelson not a smart person， she’d give all her money to the insurance broker.

如果尼爾森不是個聰明人，她會把所有的錢都投給保險經紀人。

Had he told us about the truth， we wouldn’t have come.

如果他告訴我們真相，我們就不會來了。

Had he not told us the truth， we would have blamed him.

如果他沒有告訴我們真相，我們就會責備他。

雖然要倒裝條件句有不少的規則，但是總結一下就是：倒裝后的條件句是以 should，were 或 had 之一開頭的，它們分別對應傳統條件句中的第一、二和三類條件句。了解之后，遇到此類的句子就不會驚慌失措了。