てしまう means completion and regret. It is a JLPT N4 Japanese grammar pattern used to show that an action is finished completely or happened with regret.
This grammar point often appears in daily conversation, stories, apologies, and JLPT N4 reading passages. If you want to say that something was completed or happened accidentally with an “oops” feeling, てしまう is a useful pattern to learn because it helps you read Japanese with more precision.
What does てしまう mean?
Use てしまう when you want to describe either full completion or an action the speaker feels bad about.
Natural translations include:
- do completely
- end up doing
- unfortunately do
The best translation depends on the sentence. Try to notice the writer’s or speaker’s purpose first, then choose the English phrase that fits that context.
How to form てしまう
Verb て-form + しまう / Verb で-form + しまう
Examples of the pattern:
- 食べてしまう
- 忘れてしまう
- 読んでしまう
The form before the grammar point matters. In JLPT questions, the wrong answer choices often use a similar meaning but attach it to the wrong type of word.
When is てしまう used?
Use てしまう in situations like:
- saying an action is completely finished
- expressing regret about a mistake
- describing an accidental or unwanted result
Tone and register:
- neutral; ちゃう and じゃう are casual contractions
- Common in conversation, narratives, apologies, and textbook examples
てしまう example sentences
- 宿題を全部してしまいました。 — I finished all of my homework.
- ケーキを一人で食べてしまった。 — I ended up eating the cake by myself.
- 財布を家に忘れてしまいました。 — Unfortunately, I left my wallet at home.
- 大切なメールを消してしまった。 — I accidentally deleted an important email.
- 電車の中で寝てしまいました。 — I ended up falling asleep on the train.
After reading each sentence, ask what job てしまう is doing: completion, limitation, soft denial, or summarizing a conclusion. That makes the nuance easier to remember than a one-word translation.
Nuance of てしまう
The key nuance is completion plus possible regret, depending on context.
This matters because learners often translate advanced grammar too literally. A pattern may look simple, but it can signal the writer’s attitude, the scope of a rule, or the relationship between two ideas.
For example:
- In apologies or mistakes, it sounds regretful or apologetic.
- Compared with ちゃう・じゃう, it feels more complete and less casual.
てしまう vs ちゃう・じゃう
Both てしまう and ちゃう・じゃう can express related ideas, but they are different.
てしまう:
- standard form that works in polite and written sentences
- can emphasize completion or regret
ちゃう・じゃう:
- casual spoken contractions of てしまう and でしまう
- sound lighter and more conversational
Quick contrast examples:
- 全部食べてしまいました。— I ate it all.
- 全部食べちゃった。— I ate it all / I went and ate it all.
If both translations seem possible, check the tone. Is the sentence casual, formal, written, explanatory, or emotional? The tone often tells you which grammar point is natural.
Common mistakes with てしまう
Watch out for these mistakes:
- Assuming てしまう always means regret; sometimes it only means completion
- Using ちゃう in formal writing instead of てしまう
- Forgetting that verbs ending in んで become じゃう in casual speech
A helpful practice method is to write one sentence with てしまう, then rewrite it with ちゃう・じゃう. If the meaning or tone changes, explain that difference in your own words.
Is てしまう on the JLPT?
Yes. てしまう is commonly taught as JLPT N4 grammar.
That means learners should be able to:
- recognize it in reading
- understand its nuance in context
- use it in simple original sentences
For test preparation, study the grammar point in full sentences. JLPT questions often test whether you understand the surrounding context, not just the dictionary meaning.
Practice questions for てしまう
Try making your own sentences with these prompts:
- Say you accidentally forgot your phone.
- Say you finished reading a book completely.
- Rewrite 食べてしまう in casual contracted form.
Keep your first sentences simple. Once the structure feels natural, add more context so the nuance becomes clear.
Learn てしまう with Kanjiru
If you want to review てしまう together with kanji, vocabulary, and other JLPT N4 patterns, Kanjiru helps you practice Japanese in short, focused sessions.
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