# てしまう: completion and regret > Learn how to use てしまう, a JLPT N4 Japanese grammar point meaning completion and regret, with structure, nuance, examples, mistakes, and comparisons. JLPT level: N4 · Updated: 2026-05-17 · Canonical: https://hane-app.com/blog/n4-te-shimau/ **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: - 食たべてしまう - 忘わすれてしまう - 読よんでしまう 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

宿題しゅくだいを全部ぜんぶしてしまいました。

I finished all of my homework.

completion

ケーキを一人ひとりで食たべてしまった。

I ended up eating the cake by myself.

regret

財布さいふを家いえに忘わすれてしまいました。

Unfortunately, I left my wallet at home.

accident

大切たいせつなメールを消けしてしまった。

I accidentally deleted an important email.

regret

電車でんしゃの中なかで寝ねてしまいました。

I ended up falling asleep on the train.

completion

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

Works in polite and written sentences; can emphasize completion or regret

全部ぜんぶ食たべてしまいました。

I ate it all.

ちゃう・じゃう

casual contractions

Sound lighter and more conversational

全部ぜんぶ食たべちゃった。

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

❌ Assuming てしまう always means regret

Sometimes it only means completion with no negative feeling.

✅ Decide nuance from context

宿題しゅくだいを全部ぜんぶしてしまいました simply means the homework was fully completed.

❌ Using ちゃう in formal writing

ちゃう is too casual for essays, reports, or polite speech.

✅ Use てしまう in formal contexts

Stick to てしまう or しまいました when writing or speaking politely.

❌ Forgetting で-form contractions

Verbs ending in んで do not become ～でちゃう.

✅ で-form verbs contract to じゃう

読よんでしまう becomes 読よんじゃう, not 読んでちゃう.

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.

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

1 Say you accidentally forgot your phone. regret

2 Say you finished reading a book completely. completion

3 Rewrite 食べてしまう in casual contracted form. contraction

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 Use **てしまう** as part of your **JLPT N4** て-form action-flow and auxiliary verb grammar toolkit. Review the main て-form action first, then ask what the auxiliary adds: preparation, trial, completion, regret, movement, continuation, or a change over time. Build short verb chains before using longer sentences.

Make one short sentence with てしまう without looking at the pattern chart.

Compare it with ちゃう・じゃう. Choosing between them helps you understand register and tone.

Add 終わる or ておく to the same verb and observe how the nuance changes.

For practice, write one sentence that uses てしまう in its most literal meaning, one sentence that changes the subject or time expression, and one sentence that contrasts it with one of the related patterns below.

## Related grammar to review next - [てしまう / ちゃう](/blog/n4-te-shimau-chau/) — compares another て-form auxiliary that changes action flow or completion. - [終わる](/blog/n4-owaru/) — compares another て-form auxiliary that changes action flow or completion. - [ておく](/blog/n4-te-oku/) — compares another て-form auxiliary that changes action flow or completion. - [てみる](/blog/n4-te-miru/) — compares another て-form auxiliary that changes action flow or completion. Browse more lessons here: - [All grammar lessons](/blog/) - [JLPT N4 grammar lessons](/blog/n4/) ## Learn てしまう with Hane If you want to review **てしまう** together with the related patterns above, Hane helps you practice Japanese in short, focused sessions. Browse more lessons here: - [All grammar lessons](/blog/) - [JLPT N4 grammar lessons](/blog/n4/)