1) 表示兩個動作幾乎連續發生，後子句通常立刻接在前子句之後。
2) 後面要接完整子句（主詞 + 動詞）；不可只放名詞（錯：As soon as the exam.）。
3) 談未來時，as soon as 引導的從屬子句用現在式；主句可用未來式（I will call you as soon as I get home.）。
4) 當 as soon as 子句在句首時，子句末尾加逗號；主句在前時通常不加逗號。
5) 與 when 相比，as soon as 更強調「立即、緊接著」。
合併形式範例：
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I will call you as soon as I get home.
我一到家就打給你。
其他形式：
as soon as possible
意思為「儘快」。常用於請求、指示或回覆。縮寫為 ASAP（較口語）；正式寫作建議使用完整拼寫。
ASAP
為 as soon as possible 的縮寫，口語、訊息常見；正式考試或報告不建議使用。
常見錯誤
✗
I will call you as soon as I will get home.
✓
I will call you as soon as I get home.
時間從屬子句（as soon as 引導）談未來時，用現在式，不用 will。
✗
As soon as the exam, we went to eat.
✓
As soon as the exam ended, we went to eat.
as soon as 後面需接完整子句（要有主詞與動詞），不能只放名詞片語。
✗
We go to the gym, as soon as we finish dinner.
✓
We go to the gym as soon as we finish dinner.
當主句在前、as soon as 子句在後時，通常不需要逗號；逗號在此多餘。
✗
I’ll finish ASAP in my formal report.
✓
I will finish as soon as possible in my formal report.
ASAP 偏口語，正式寫作建議改用完整的 as soon as possible。
同義詞與反義詞
同義
once
(一旦)
語氣較中性，側重「條件一成立就…」，未特別強調「立刻」；常與 as soon as 可互換。
同義
the moment (that)
(一…就…；當…的那一刻)
口語色彩較強，語氣更生動；時態規則同 as soon as。
同義
right after
(在…之後立刻)
偏副詞/介系詞用法，常接名詞或動名詞（Right after class / right after finishing…），語氣非常即時。
同義
immediately after
(在…之後立刻)
語氣較正式，結構與 right after 類似，強調緊接發生。
同義
no sooner ... than
(一…就…)
較正式且需倒裝（No sooner had S p.p. than S V-ed），常用於書面或強調語境。