but then的音標是[b?t een]，基本翻譯是“但是，而且;既然;不過”。速記技巧是將其拆分為單詞but和then來記憶。

But then 的詞源：

But 是連詞，表示轉折關系，而 then 是副詞，表示“然后”的意思。這兩個詞都是古英語時期引入的詞匯。

變化形式：But 通常沒有變化形式，而 then 可以根據語境和搭配的不同而變化，如 then 和 than 連用時，then 可以變為過去分詞形式。

相關單詞：

1. until 和 till 是與 but 和 then 相關的詞匯，它們都表示時間上的轉折關系。

2. before 和 after 也是與 but 和 then 相關的詞匯，它們表示時間上的先后順序。

3. again 和 over 是與 then 相關的詞匯，表示重復或再次的意思。

例句：

1. We waited for an hour, but then we decided to leave.（我們等了一個小時，但是后來我們決定離開。）

2. I didn"t sleep well last night, but then again, I was nervous about the exam.（昨晚我沒睡好，但是再一想，我對考試很緊張。）

3. After finishing my work, I took a break, but then I realized I had forgotten to do something.（完成工作后我休息了一下，但是后來我發現我忘了做某件事。）

總之，but 和 then 這兩個詞在英語中經常使用，它們表示轉折和時間上的先后順序關系，是英語中非常重要的連詞和副詞。

常用短語：

1. but then again

2. but even so

3. but on the other hand

4. but nevertheless

5. but eventually

6. but in the end

7. but then and again

例句：

1. But then again, we all have our own unique challenges to face.

2. But even so, I"m still determined to pursue my dream.

3. But on the other hand, I"m not giving up easily.

4. But nevertheless, I"m going to try my best to overcome this obstacle.

5. But eventually, I"m going to succeed in achieving my goal.

6. But in the end, I realized that persistence is the key to success.

7. But then and again, I wonder if I"m making the right decision.

英文小作文：

Life is full of ups and downs, but then again, it"s what we make of it that matters. Sometimes we face challenges that seem insurmountable, but with persistence and determination, we can overcome them and emerge stronger than before. However, life also brings us moments of joy and happiness, and these moments are what make life worth living. We should cherish every moment of our lives, no matter what challenges we face, because life is a journey worth taking.