てしまう — Completely Done / Regrettably Did
Indicates an action was carried through to completion — often with a nuance of regret, unexpectedness, or accident, and sometimes simply total completion.
Structure
[Verb te-form] + しまう
Examples
宿題を忘れてしまいました。
Shukudai o wasurete shimaimashita.
I ended up forgetting my homework. (regret)
忘れて + しまいました = forgot (regrettably)
本を全部読んでしまった。
Hon o zenbu yonde shimatta.
I finished reading the whole book.
読んで + しまった = read it all the way through (completion)
電車の中でさいふをなくしてしまいました。
Densha no naka de saifu o nakushite shimaimashita.
I ended up losing my wallet on the train. (accident/regret)
なくして + しまいました = lost it (accident + regret)
• Casual contractions: 〜てしまう → 〜ちゃう; 〜でしまう → 〜じゃう. • Very common: 食べちゃった (I ended up eating it), 忘れちゃった (I forgot it). • The contraction sounds more natural in casual spoken Japanese.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones てしまう is tested against.
vs ておく
てしまう = an action completed, often unintended/regretted; ておく = an action done deliberately in advance for future benefit.
vs てみる
てみる = try an action to see the result; てしまう = the action ends up fully done (frequently by accident).
More verb forms
- てくる — Come Doing / Has Been Doing (Toward Now)
- てみる — Try Doing (and See)
- Potential Form — Can / Be Able To (Verbs)
- がる／がっている — Describing Others' Feelings
- 〜出す (だす) — Abrupt Eruptions
- 〜始める (はじめる) — Intentional Beginnings
- 意向形 (いこうけい) — Volitional Form (Let's / I'll)
- くする / にする — Make something become (a quality)
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