# てしまう / ちゃう: finish completely; do accidentally > Learn how to use てしまう / ちゃう, a JLPT N4 Japanese grammar point meaning finish completely; do accidentally, with structure, nuance, examples, mistakes, and comparisons. JLPT level: N4 · Updated: 2026-05-18 · Canonical: https://hane-app.com/blog/n4-te-shimau-chau/ **てしまう / ちゃう** means **finish completely; do accidentally**. It is a **JLPT N4** Japanese grammar pattern used to express that an action was completed, often with a sense of regret, accident, or thoroughness. **しまう** is the standard form, while **ちゃう** is the casual spoken contraction. You will hear both in daily conversation and see **てしまう** in writing and polite speech. ## What does てしまう / ちゃう mean? Use **てしまう / ちゃう** when you want to express that an action was carried out fully, happened by accident, or produced a regrettable result. Natural translations include: - finish completely - do something accidentally - end up doing The best choice depends on context. If the speaker simply completed a task, "finish completely" fits. If the result was unintentional, "do accidentally" or "end up doing" is more natural. ## How to form てしまう / ちゃう

Verb て-form + しまう

Verb て-form + ちゃう

Examples of the pattern: - やってしまう - 食べちゃう - 忘れてしまいました The verb must be in the て-form before attaching **しまう** or **ちゃう**. In test questions, distractors often attach the auxiliary to the wrong stem. ## When is てしまう / ちゃう used? Use **てしまう / ちゃう** in situations like: - expressing that an action is fully completed - describing an accident or unintended result - adding a feeling of regret or resignation - softening or sharpening tone depending on whether you use **しまう** or **ちゃう** Tone and register: - **てしまう** is neutral and fits polite, written, and spoken Japanese - **ちゃう** is casual and appears mainly in spoken Japanese among friends and family - Both are common in JLPT N4 reading and listening materials ## てしまう / ちゃう example sentences

宿題しゅくだいを全部ぜんぶやってしまいました。

I finished all of my homework.

completion

財布さいふを忘わすれてしまいました。

I accidentally forgot my wallet.

accident

ケーキを全部ぜんぶ食べちゃった。

I ate the whole cake.

casual completion

大切たいせつなメールを消けしてしまいました。

I accidentally deleted an important email.

regret

この本ほんを一日いちにちで読よんでしまいました。

I finished reading this book in one day.

completion

After reading each sentence, ask whether **てしまう / ちゃう** signals completion, accident, or regret. That question makes the grammar easier to remember than a one-word translation. ## Nuance of てしまう / ちゃう The key nuance is that the action is done thoroughly or irreversibly, and the speaker often feels something about the result. This matters because **てしまう** is not simply "finish." It can imply: - relief that a task is done - regret that something happened - resignation about an unintended outcome **ちゃう** packs the same nuance into casual speech. Because it is contracted and colloquial, it can sound playful, embarrassed, or lightly frustrated depending on intonation. Read the whole sentence before choosing an English translation. ## てしまう / ちゃう vs ちゃう The two forms share the same core meaning but differ in register. **てしまう**: - standard, neutral form - used in polite speech, essays, and formal contexts - example: 宿題しゅくだいを全部ぜんぶやってしまいました。 **ちゃう**: - casual spoken contraction - used with friends, family, and in informal writing - example: ケーキを全部ぜんぶ食べちゃった。 If you are speaking to a teacher or writing a report, use **てしまう**. If you are chatting with a close friend, **ちゃう** is natural. ## Common mistakes with てしまう / ちゃう

❌

Attaching しまう to the plain dictionary form of a verb

✅

Attaching しまう to the て-form

❌

Translating every てしまう as "accidentally"

✅

Choosing "finish completely" when the context is simple completion

❌

Using ちゃう in formal writing or polite speech

✅

Using てしまいました in formal situations

A helpful practice method is to write one sentence with **てしまう**, then rewrite it with **ちゃう** and notice how the tone shifts. ## Is てしまう / ちゃう on the JLPT? Yes. **てしまう / ちゃう** is commonly taught as **JLPT N4** grammar.

Recognize てしまう and ちゃう in reading and listening
Understand whether the nuance is completion, accident, or regret
Choose the correct form for polite and casual contexts

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 / ちゃう

1 Write one short sentence using てしまう to describe an accident or regrettable action. accident

2 Rewrite the same idea using ちゃう to make it casual. register

3 Compare your sentence with 終わる and note the difference in tone. comparison

Keep your first sentences simple. Once the structure feels natural, add more context so the nuance becomes clear. ## Learning path for てしまう / ちゃう To learn **てしまう / ちゃう** efficiently, start with its formation, then compare registers, and finally practice in context.

1 Review the て-form for verbs you know well.

2 Attach しまう to a verb and say the sentence out loud.

3 Rewrite the sentence with ちゃう and notice the register shift.

4 Contrast the same idea with 終わる or ておく to feel the nuance change.

5 Write three original sentences: one about completion, one about an accident, and one that is casual.

## Related grammar to review next - [終わる](/blog/n4-owaru/) — neutral completion without the emotional weight of てしまう - [ておく](/blog/n4-te-oku/) — preparation done in advance - [てみる](/blog/n4-te-miru/) — trying something out Browse more lessons here: - [All grammar lessons](/blog/) - [JLPT N4 grammar lessons](/blog/n4/) ## Learn てしまう / ちゃう with Hane If you want to review **てしまう / ちゃう** together with the related patterns above, Hane helps you practice Japanese in short, focused sessions. [Start practicing with Hane](/)