Some actions in life are accidents. Others are done completely. Japanese has a simple expression that can capture both meanings depending on the context: ～てしまう. This grammar point is a great tool for expressing either regret or total completion of an action so you can tell someone you dropped your phone by mistake, or that you finished reading an entire textbook.
～てしまう
To do something accidentally or completely
Usage Pattern
[Verb in て-form] + しまう
[Verb in て-form] + ちゃう(casual contraction)
[Verb in で-form] + じゃう(casual contraction)
Details
JLPT Level: N4–N3
How to Use It
Use ～てしまう when something happens unintentionally or when you want to emphasize that something is done in full. The verb しまう follows the て-form of the main verb. In casual conversation, しまう is often shortened to ちゃう or じゃう. Which meaning is intended accident or completion, depends on the context of the sentence.
Want A Deeper Explanation?
Example 1
ごめんなさい。名前を忘れてしまいました。
ごめんなさい。なまえ を わすれて しまいました。
Gomen nasai. Namae o wasurete shimaimashita.
I’m sorry. I forgot your name.
Example 2
ケーキを全部食べてしまった。
けーき を ぜんぶ たべて しまった。
Kēki o zenbu tabete shimatta.
I ate the entire cake.
Example 3
コップを割っちゃった。
こっぷ を わっちゃった。
Koppu o wacchatta.
I broke the cup (by accident).