What is てしまう?
てしまう is one of those patterns that carries two distinct feelings, and context tells you which one is in play. The first: you did something completely, all the way through. The second: something happened that you regret, or that was accidental or unfortunate. Sometimes both at once.
Take the て form of a verb and add しまう. That's the structure. The nuance is where things get interesting.
The Two Meanings
1. Completion -- "finished doing ~"
てしまう can express that an action was carried out fully, with nothing left undone:
- 本を全部読んでしまった。
I read the entire book. (finished it) - 宿題をやってしまった。
I finished all the homework.
You'll often see it with words like すっかり (completely), 全部 (all), or 完全に (entirely) when this is the intended meaning.
2. Regret / Unfortunate result -- "did ~ (oops)"
This is probably the more common usage in conversation. てしまう signals that something happened and the speaker is not happy about it:
- 財布を忘れてしまった。
I (accidentally) forgot my wallet. - 雨が降ってしまった。
It rained (unfortunately).
The regret can range from a minor "oops" to genuine distress. The speaker didn't want this to happen, or they feel bad about it.
How to Tell the Meanings Apart
Context does the heavy lifting. If the sentence is about accomplishing or finishing something, it's completion. If the tone suggests something went wrong or was unintended, it's regret. Sometimes both feelings overlap -- "I ate the whole cake" can be both an accomplishment and a source of guilt.
Conjugation
しまう is a u-verb, so it conjugates normally. Here's how it looks in past tense:
| Form | Japanese |
|---|---|
| Present | 食べてしまう |
| Past (casual) | 食べてしまった |
| Past (polite) | 食べてしまいました |
| Negative | 食べてしまわない |
The past tense てしまった is especially common -- you're usually talking about something that already happened.
Casual Contractions: ちゃう and じゃう
In spoken Japanese, てしまう almost always gets shortened. This is not slang; it's standard casual speech:
| Full Form | Contraction |
|---|---|
| てしまう | ちゃう |
| でしまう | じゃう |
| てしまった | ちゃった |
| でしまった | じゃった |
So 食べてしまった becomes 食べちゃった. 飲んでしまった becomes 飲んじゃった.
These contracted forms (ちゃう, じゃう) conjugate as regular u-verbs: ちゃう, ちゃった, ちゃわない, etc. You'll hear ちゃう and じゃう far more often than the full てしまう in casual conversation.
てしまう vs ている
Don't mix these up. ている describes an ongoing state or action in progress. てしまう emphasizes that something is done, finished, or happened regrettably. Compare:
- 食べている
I am eating (in progress) - 食べてしまった
I ate it all / I ate it (and I shouldn't have)
Example Sentences
-
ケーキを全部食べてしまった。 (keeki wo zenbu tabete shimatta.)
I ate all the cake. (completion + maybe regret) -
電車に乗り遅れちゃった。 (densha ni noriokurechatta.)
I missed the train. (regret) -
大事なファイルを消してしまいました。 (daiji na fairu wo keshite shimaimashita.)
I accidentally deleted an important file. -
あの映画、もう見ちゃった？ (ano eiga, mou michatta?)
Did you already watch that movie? -
彼女に秘密を言ってしまった。 (kanojo ni himitsu wo itte shimatta.)
I let the secret slip to her. (regret) -
すっかり忘れちゃった。 (sukkari wasurechatta.)
I completely forgot. (regret) -
レポートを書いてしまいましょう。 (repooto wo kaite shimaimashou.)
Let's finish writing the report. (completion) -
雨が降ってきちゃった。 (ame ga futtekichatta.)
It started raining. (unfortunate)