The ～ておく Form in Japanese: Doing Something in Advance (and Leaving It Be)

The ～ておく form in Japanese attaches to a verb's te-form. It says you are doing something now and setting its result in place for later.¹ It is one of the first te-form auxiliaries an N4 learner picks up. Its two readings, "do in advance" and "leave it as it is," both come from a single verb.²

Overview

Where ～ておく sits

～ておく is an N4 grammar point and one of the core te-form auxiliaries.¹³ It attaches to the te-form of a verb plus おく, where おく is the lexical verb 置く ("to put / place").¹

When it functions as the te-form auxiliary, ～ておく is normally written in kana (おく), not in kanji. The kanji 置く is reserved for the literal "place" verb.¹ Dictionaries record the auxiliary sense under the headword 置く but mark it as the 補助動詞 (auxiliary-verb) use.²

The register is neutral everyday Japanese. Use the full form ～ておきます in polite and written contexts. The contracted form ～とく appears in casual speech.¹⁴

The one core idea

The lexical verb 置く carries two linked senses that the auxiliary inherits: positioning a person or object in a certain place, and keeping a state going (leaving something as it is).² 精選版日本国語大辞典 records this second sense for 置く as "leaving something in a certain state; leaving it untouched."⁵

Both auxiliary readings come from this one verb. デジタル大辞泉 lists the 補助動詞 ～ておく under exactly two sub-senses: ㋐ doing something in advance for the sake of future readiness, and ㋑ keeping that state going, leaving it as is.²

So the "prepare / do in advance" reading and the "leave as is" reading are not two unrelated grammar points. They are two sides of 置く ("set down, and let stay") recorded in a single dictionary entry.²

Both readings live in one dictionary entry

デジタル大辞泉 files ㋐ "do in advance" and ㋑ "leave as is" under the same 補助動詞 headword. That is the evidence that you are learning one auxiliary, not two. Many study pages teach the two senses as separate points.²

The diagram below shows how the single verb branches into the two uses this article covers.

Here is a short example of each reading before the form section:

話はなしだけは聞きいておこう。²
"Let me at least hear them out first."

窓まどを開あけておく。²
"I'll leave the window open."

Form: how to build ～ておく

The rule: te-form + おく

The formation is verb te-form + おく.¹³ おく conjugates as an ordinary 五段 (godan / u-verb) verb. Its main forms are おきます (polite), おいた (past), おかない (negative), おけば (conditional), and おこう (volitional).¹

旅行りょこうの前まえに切符きっぷを買かっておきます。³
"I'll buy the tickets before the trip."

The で-voicing some learners expect is not a separate rule for おく. It comes from the te-form itself. Verbs whose te-form is voiced (the -ぶ / -む / -ぬ and -ぐ groups, such as 飲む → 飲んで and 読む → 読んで) keep that で and simply add おく.⁶

本ほんを読よんでおく。⁶
"I'll read the book beforehand."

A learner who already produces 飲んで needs no new table; おく just appends.⁶

ビールを冷ひやしておく。¹
"I'll chill the beer in advance."

Conjugation across tense and polarity

The auxiliary おく inflects. The te-form before it does not change.¹ The past ～ておいた / ～ておきました reports a completed advance-action: something was done ahead of time and the result stands.³

Form	Build	Reading	Function
～ておく	te-form + おく	-te oku	plain non-past1
～ておきます	te-form + おきます	-te okimasu	polite non-past1
～ておいた	te-form + おいた	-te oita	plain past: advance-action done3
～ておきました	te-form + おきました	-te okimashita	polite past: advance-action done3
～ておかない	te-form + おかない	-te okanai	plain negative1
～ておこう	te-form + おこう	-te okō	volitional: "let me get this done in advance"7

来週らいしゅうの試験しけんのため、漢字かんじを勉強べんきょうしておきました。³
"I studied my kanji in advance for next week's exam."

出でかける前まえに何なにか食たべておこう。³
"Let's eat something before we head out."

The two main uses

Use 1: do it in advance (preparation)

This is the dominant reading: do something now to be ready for a later need.²³ デジタル大辞泉 defines it as doing something in advance for the sake of future readiness.²

Japanese teaching often splits this advance-action reading into two motives. These are reasons a speaker reaches for the form, not hard grammatical categories. The same sentence can fit either motive depending on why the speaker acts.⁸

• 準備, preparation that enables a later need: doing the necessary groundwork for a purpose, such as booking ahead, buying ahead, or studying ahead.³⁸
• 措置 / 予防, action that pre-empts a future problem: acting now so an undesired situation does not arise.⁸ Tofugu states the same split: one acts in advance either to enable a desired outcome or to prevent an undesirable one.⁷

Both motives use the same grammatical form. Only the speaker's reason differs: achieving something later versus avoiding something later.⁸⁷

来月らいげつ、北海道ほっかいどうに行いくから、ホテルを予約よやくしておきます。⁶
"I'm going to Hokkaido next month, so I'll book a hotel in advance."

食事しょくじが終おわったら、お皿さらを洗あらっておきます。⁸
"Once the meal is over, I'll wash the dishes to have it taken care of."

The boundary between the two motives is soft. Opening a window because it is hot can be read as 措置 (pre-empting the heat). It can also be filed under simply maintaining a comfortable state. That is why the sources do not always agree on where a given sentence lands.⁸

暑あついので、窓まどを開あけておきます。⁸
"Since it's hot, I'll open the window and leave it open."

The volitional ～ておこう means "let me get this done in advance." It is a common self-prompt in this preparation reading.³⁷

Use 2: leave it as it is (let it be)

The second recorded sense is to keep a state going, or to leave it as is. デジタル大辞泉 gives this as その状態を続けさせる ("keep that state going"), with the example 窓を開けておく ("leave the window open").²

This reading covers two cases: leaving an existing state untouched, and doing an action and then deliberately leaving the result standing, such as turning a light on and leaving it on.⁷ Japanese teaching materials label it 放置 / 現状維持, maintaining the present state without doing anything to change it.⁸⁶

そのままにしておいてください。⁷
"Please leave it as it is."

先生せんせい、ホワイトボードは消けさずにそのままにしておいてください。⁶
"Teacher, please leave the whiteboard as it is without erasing it."

このまま寝ねかせておいてあげよう。⁷
"Let's just let her keep sleeping."

Why both senses are one verb

置く means "put something down, and let it stay there."² The auxiliary keeps both halves of that meaning. The two main uses simply foreground different halves.²

The "prepare / do in advance" reading foregrounds the putting: you carry out an action now and set its result in place for later.² The "leave as is" reading foregrounds the staying: a state remains unchanged.²⁵

Bunpro states the same dual core for the verb itself. It glosses 置く as "to place something down" while also noting the nuance "to leave something alone."¹ This is why a single dictionary entry covers both readings of ～ておく.²

The casual contraction: ～とく and ～どく

～ておく → ～とく, ～でおく → ～どく

In casual speech, ～ておく contracts to ～とく, and the voiced ～でおく contracts to ～どく.¹⁴ So やっておく becomes やっとく, and 見ておく becomes 見とく. The voiced 読んでおく becomes 読んどく.¹⁷⁴

あとは片付かたづけとくから。⁴
"I'll take care of cleaning up the rest, so don't worry."

その本ほん、読よんどくね。⁴
"I'll read that book beforehand, okay?"

Keep the contraction out of formal writing

～とく and ～どく are everyday spoken contractions, comparable to English "wanna" and "gonna." They are not slang.⁴ They are correct casual Japanese, but written and formal contexts keep the full ～ておく form.⁴

Contraction across the conjugation

The contraction carries through the conjugation in parallel with the full form. The past, te-form, negative, and volitional all have a contracted counterpart.⁴

Full form	Contracted	Function
～ておく	～とく	plain non-past4
～ておいた	～といた	past4
～ておいて	～といて	te-form / request (～といてください)4
～ておかない	～とかない	negative4
～ておこう	～とこう	volitional4
～でおく (voiced)	～どく	voiced-stem non-past14

ちょっと言いっといてね。⁴
"Go ahead and tell them in advance, okay?"

Nuance and usage contexts

Register: where each form fits

Use the full polite ～ておきます for polite speech and writing. The contracted ～とく is casual-speech only.¹⁴ The volitional ～ておこう functions as a common self-directed prompt, "let me get this done in advance."³⁷

このトピックは、この辺へんで終おわりにしておきましょう。⁷
"Let's wrap this topic up around here and leave it there."

～ておく vs ～てある: the boundary

Both forms can describe a result that stands because of an earlier deliberate action. That is why learners confuse them.⁷

～ておく foregrounds the agent's deliberate, forward-looking action: "I do X now, for later." It names the act of preparing.²⁷

～てある foregrounds the resulting state with the agent backgrounded: "X has been done and is in place." It names the standing result, with the doer left unstated.⁷

切符きっぷを買かっておきました。³
"I bought the tickets in advance." (names the action taken)

切符きっぷが買かってあります。⁷
"The tickets are bought and ready." (names the standing state)

The two are linked, not identical. A ～てある state can be re-described as the result of a ～ておきました action. One names the preparing. The other names the state that preparing left behind. The full transitivity and agent comparison belongs with the dedicated ～ている / ～てある treatment rather than here.⁷

Good to know

Anchor both readings on the kanji 置

The kanji 置 anchors both readings of the auxiliary. Dictionaries of record list 置く with both a "set in place" sense and a "leave in a state" sense. Bunpro phrases it as "to place something down" plus "to leave something alone."²⁵¹ Keeping the lexical verb in mind stops "do in advance" and "leave as is" from feeling like two unrelated grammar points. They are the putting-half and the staying-half of one verb.²

Reading ～ておく over-literally as "put"

As an auxiliary, おく has moved away from the literal "place" meaning, and the dictionary lists it as a 補助動詞 sense distinct from the literal verb.² Reading 確認しておく as "put a confirmation" misreads the form. It means "I'll confirm it in advance." The correct reading keeps the advance-action sense, not physical placement.

確認かくにんしておく。²
"I'll confirm it in advance."

Mistaking 言っとく for the particle と plus a verb

言っとく is the casual contraction of 言っておく ("I'll tell them in advance"), not と (the quote particle) plus a separate verb.⁴ The contraction is frequent in casual speech and appears on many verbs, such as やっとく, 見とく, and 言っとく. A learner who parses the と as the quotative particle will misread the sentence. The contraction is ～ておく → ～とく.¹⁴

The で in 読んでおく is automatic, not a new rule

The voiced で in 読んでおく, 飲んでおく, and 飛んでおく comes from the te-form of those verbs (読んで, 飲んで, 飛んで), not from おく.⁶ If you already produce 飲んで, you simply append おく. There is no separate でおく conjugation to memorize. The contraction then voices in parallel: 読んでおく becomes 読んどく.¹⁴

See also

• The ～てしまう Form in Japanese: Completion, Regret, and the Casual ちゃう / じゃう
• The ～てくる / ～ていく Form in Japanese: Directional and Temporal Movement
• The ～ている Form in Japanese: Progressive vs. Resultant State
• Tense, Aspect, and Mood in Japanese: A Map
• The ～まま Grammar Point: "As-Is" and "Without Changing" in Japanese

References

Footnotes

1. Bunpro. Grammar point「ておく」(JLPT N4). https://bunpro.jp/grammar_points/%E3%81%A6%E3%81%8A%E3%81%8F ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰

2. デジタル大辞泉 (Shogakukan). Entry「置く」, 補助動詞 sense, via Kotobank. https://kotobank.jp/word/%E7%BD%AE%E3%81%8F-451670 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹

3. JLPTsensei. "JLPT N4 Grammar: ておく (te oku) Meaning." https://jlptsensei.com/learn-japanese-grammar/%E3%81%A6%E3%81%8A%E3%81%8F-te-oku-meaning/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³

4. Maggie Sensei. "Casual Contraction: dropping the い / ～とく." https://maggiesensei.com/2016/03/28/casual-contraction-dropping-%E3%81%84-i-%E3%81%A6%E3%82%93-ten-%E3%81%A8%E3%81%8Ftoku/ (limitation) ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹

5. 精選版 日本国語大辞典 (Shogakukan). Entry「置く」, "leave in a state" sense, via Kotobank. https://kotobank.jp/word/%E7%BD%AE%E3%81%8F-451670 ↩ ↩² ↩³

6. 日本語教師ネット (nihongokyoshi-net.com). 「【JLPT N4】文法・例文：Vておく」. https://nihongokyoshi-net.com/2018/09/19/jlptn4-grammar-teoku/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

7. Tofugu. "〜ておく: To Do Something for Future Convenience." https://www.tofugu.com/japanese-grammar/teoku/ (limitation) ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵

8. たのすけ (tanosuke.com). 「『～ておく』の準備・措置・放置の違いと3つのポイント」. https://tanosuke.com/teoku ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸