“〜te shimau”: Completely Did / Accidentally / Regret [JLPT N4]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

財布を忘れてしまった・食べてしまった — the completion nuance, regret nuance, and colloquial contraction of てしまう.

「宿題をやってしまった」 — “finished it” or “oh no”? The two faces of 「〜てしまう」

「宿題を全部やってしまった」 can be the relief of “(finally) got it all done,” or in another sentence the chagrin of “oh no, by accident” — 「(verb て-form) ＋ しまう」 has two feels: ① completion (fully finished); ② by accident, regret. Told by context and whether the event is positive or negative. This guide covers 「てしまう」's two senses, the colloquial contraction 「ちゃう／じゃう」, and how it fits among the other て-auxiliaries (comparison: 〈てみる complete〉 guide).

Core: completion (thorough)／by accident (regret)

「〜てしまう」 has two feels:

• ① Completion, thoroughly done (neutral, satisfying): 宿題をやってしまう (get the homework done), 読んでしまう (finish reading).
• ② By accident, regret (negative): 財布を落としてしまった (accidentally dropped my wallet), 遅刻してしまった (ended up late).

Test: good/neutral = completion; bad/slip = by accident, regret. Colloquially 「〜ちゃう／〜じゃう」.

How to Connect

例句與情境

• 宿題を全部やってしまった！これで安心。(Got all my homework done! Now I can relax.) — completion (relief)
• あー、スマホを落としてしまった。(Ugh, I dropped my phone.) — by accident
• 面白くて、一晩で読んでしまった。(It was so good I finished it in one night.) — completion
• 電車で寝過ごしてしまった。(I overslept my stop on the train.) — regret
• あ、ケーキ食べちゃった。(Oh, I ate the cake.) — colloquial (ちゃう)

⚠️ Where learners slip up

① The two senses by “positive/negative.” Neutral/good = “(just) get it done” (宿題をやってしまおう = let's get the homework done); bad/slip = “by accident, oh no” (財布をなくしてしまった = accidentally lost it). The same てしまう, worlds apart in tone — by the nature of the event.

② The colloquial 「ちゃう／じゃう」 is super frequent. 〜てしまう→〜ちゃう (食べちゃう, 忘れちゃう), 〜でしまう→〜じゃう (飲んじゃう, 読んじゃう). Casual speech almost always uses them — your listening must catch “ちゃった = てしまった.”

③ The chagrin of “by accident” is the point. Often てしまう conveys “ugh, oh no, I shouldn't have” (遅刻しちゃった = ended up late, with chagrin). English often maps to “ended up ~ing, accidentally ~, went and ~.”

🔄 Compare with similar forms: てしまう／ちゃう／きる

💡 The key point in use

「てしまう」 has two faces, told by whether the event is positive or negative: good/neutral = “(just, thoroughly) get it done” (全部食べてしまおう = let's finish it off); bad/slip = “by accident, oh no, regret” (寝坊してしまった = overslept by accident). Most important daily is the colloquial contraction: 〜ちゃう (= てしまう), 〜じゃう (= でしまう) — 「遅刻しちゃった (ended up late)」, 「全部食べちゃった (ate it all up)」 are super frequent; you must understand and produce them. Often てしまう conveys that “ah… (chagrin/resignation)” feeling — a very human expression. For comparison with other て-auxiliaries (てみる／ておく), see the 〈てみる complete〉 guide.

❓ Questions you might have

Q: Is 「てしまう」 “finish” or “by accident”?

Both — tell by the event's positive/negative nature and context. ① Completion, thoroughly done (neutral, satisfying): 宿題を全部やってしまった ((finally) got it all done), 面白くて一気に読んでしまった (so good I read it in one go) — stressing “completion, wrapping up.” ② By accident, regret (negative): 財布を落としてしまった (accidentally dropped my wallet), 大事な約束を忘れてしまった (went and forgot an important promise) — with chagrin. Test: good/neutral = finish; bad/slip = by accident, oh no.

Q: What are 「ちゃう」「じゃう」? Same as 「てしまう」?

Same — the colloquial contractions. 「〜てしまう」→「〜ちゃう」 (食べてしまう→食べちゃう, 忘れてしまう→忘れちゃう); 「〜でしまう」→「〜じゃう」 (飲んでしまう→飲んじゃう, 読んでしまう→読んじゃう). Past: 〜ちゃった／じゃった (食べちゃった = ate it up, 遅刻しちゃった = ended up late). Casual speech almost always uses the contraction; formal/written uses the full 「てしまう」. For listening and speaking, get used to “ちゃう = てしまう.”

🖊️ Practice Questions (5)

Q1. 「あー、スマホを落として___。」 (oops, I dropped my phone) Which fits the blank?

(A) みた　(B) しまった　(C) おいた　(D) ある

Q2. What is the colloquial contraction of 「てしまう」 (て + しまう)?

(A) てる　(B) とく　(C) ちゃう　(D) ておく

Q3. 「宿題を全部やって___！」 (a sense of completion, relief) Which is most appropriate?

(A) しまった　(B) みた　(C) いる　(D) おいた

Q4. What is the colloquial contraction of 「飲んでしまう」?

(A) 飲んちゃう　(B) 飲んじゃう　(C) 飲んしまう　(D) 飲んとく

Q5. What is the nuance of 「全部食べてしまいたい」?

(A) 誤って全部食べた

(B) ate it all in advance

(C) want to eat it all (expressing a feeling)

(D) try eating it all

Answer Explanations

1. (B) しまった ── 「落としてしまった」 = accidentally dropped the phone (a nuance of regret).

2. (C) ちゃう ── てしまう → ちゃう (colloquial contraction, unvoiced て: 食べてしまう→食べちゃう).

3. (A) しまった ── 「やってしまった！」 = got it done! (a relaxed sense of completion). Here it's a positive nuance (the homework is finished).

4. (B) 飲んじゃう ── でしまう → じゃう (colloquial contraction, voiced で: 飲んでしまう→飲んじゃう).

5. (C) want to eat it all ── 〜てしまいたい = really want to get it done (expressing a feeling). Not "already did it" but "really want to do it".