～てしまう (completion/regret)

• Reading: しまう
• Romaji: shimau
• Formation: Verb て-form + しまう/しまいます

Meaning

An auxiliary verb attached to the て form of a verb to express the complete finishing of an action. It often carries an additional nuance of regret, disappointment, or the idea that something happened unintentionally or unfortunately.

てしまう has two main uses. First, it marks that an action has been carried through to completion, emphasizing the thoroughness or finality of the result — for example, finishing all of a meal or reading an entire book. Second, and more commonly in conversation, it conveys that something regrettable or unintended happened, like losing a wallet or accidentally saying something hurtful. In casual speech, てしまう contracts to ちゃう (and でしまう to じゃう), which is extremely common and important for comprehension. The polite form is てしまいます. Learners sometimes overuse this pattern for neutral completed actions where simple past tense suffices.

Examples

1. 宿題を全部やってしまった。 I finished all of my homework.
2. 大事な書類をなくしてしまいました。 I lost an important document.
3. 電車の中で寝てしまった。 I fell asleep on the train.

Usage Guide

Context: spoken, written, everyday

Tone: emotive

Do Say

• 彼女に秘密を話してしまった。
• この小説は一日で読んでしまいました。
• 財布を忘れてしまって困りました。
• 約束の時間に遅れてしまいました。

Don't Say

• 毎日ご飯を食べてしまいます。(Using てしまう for a routine action with no sense of completion or regret) → 毎日ご飯を食べます。
• 昨日しまって勉強した。(Placing しまう before the main verb instead of after the て form) → 昨日勉強してしまった。
• 電話をかけしまった。(Omitting the て form — must be かけてしまった) → 電話をかけてしまった。

Origin & History

しまう originally meant 'to put away' or 'to store,' implying an action is done and put to rest. This sense of finality extended to mean completion of any action, and the regret nuance emerged from the feeling of irreversibility.

Cultural Context

Generation: All ages

Social background: Universal