Japanese Te-Form Auxiliaries: Oku, Shimau, Miru, Kuru

The te-form by itself means almost nothing. 食べて (tabete, "eat (te-form)") on its own is a fragment. Its real job is to be a hub: it is the shape a verb takes when something else is about to attach to it, and what attaches determines what the verb means.

Those attachments are called auxiliary verbs, and there are a dozen or so you will meet constantly. They never change the core meaning of the verb. They add a layer: in advance, by accident, on purpose to see, toward me, away from me, while also doing something else. Learn them as a set and your Japanese stops sounding like translated English.

Everything here builds on the te-form itself, so make sure the conjugation is automatic before you work on the meanings.

The full set at a glance

ておく (te-oku): do it in advance

ておく marks an action done now so that it pays off later. The English translation is usually "in advance", "ahead of time", or "and leave it that way".

• 会議の前に資料を読んでおきます (kaigi no mae ni shiryou o yonde okimasu) — "I'll read the materials before the meeting." (i.e. ahead of time, so I'm ready)
• ビールを冷やしておきます (biiru o hiyashite okimasu) — "I'll chill the beer." (and leave it cold for when you arrive)
• 窓を開けておいてください (mado o akete oite kudasai) — "Please leave the window open."

In casual speech ておく contracts hard: ておく becomes とく and ておいて becomes といて.

• 買っておく (katte oku) becomes 買っとく (kattoku) — "I'll buy it ahead of time"
• 開けておいて (akete oite) becomes 開けといて (aketoite) — "leave it open"

You will hear 買っとく far more often than the full form in actual conversation. Also common is the idiom 放っておく (houtte oku) — "leave it alone".

てしまう (te-shimau): completion, and regret

てしまう has two related senses and English separates them, which is why learners find it slippery.

Sense one: done completely. ケーキを全部食べてしまいました (keeki o zenbu tabete shimaimashita) — "I ate the whole cake." Nothing went wrong; the emphasis is that it is finished, entirely.

Sense two: done, unfortunately. 財布を忘れてしまいました (saifu o wasurete shimaimashita) — "I forgot my wallet, damn." Here the auxiliary carries regret, and there is no English word doing that job, so English speakers usually drop it.

• 宿題を忘れてしまった (shukudai o wasurete shimatta) — "I forgot my homework." (with a sinking feeling)
• 電車に乗り遅れてしまいました (densha ni noriokurete shimaimashita) — "I missed the train." (and I'm annoyed about it)

In casual speech てしまう contracts to ちゃう and でしまう to じゃう:

• 忘れてしまった (wasurete shimatta) becomes 忘れちゃった (wasurechatta)
• 飲んでしまった (nonde shimatta) becomes 飲んじゃった (nonjatta)
• 食べちゃだめ (tabechadame) — "Don't you dare eat it."

てみる (te-miru): try it and see

てみる comes from the verb 見る (miru, "see"), and it keeps a trace of that: you do something in order to find out what happens.

• 食べてみます (tabete mimasu) — "I'll try it" (said about unfamiliar food)
• 聞いてみてください (kiite mite kudasai) — "Try asking."
• 一度やってみたいです (ichido yatte mitai desu) — "I'd like to try it once."

食べてみる is not "eat", it is "try eating". If you drop the みる you lose the experiment.

てくる (te-kuru) and ていく (te-iku): direction and time

These two use the actual verbs くる (kuru, "come") and いく (iku, "go"), and they work on two axes at once.

Space: movement toward or away from the speaker.

• 犬が走ってきました (inu ga hashitte kimashita) — "The dog came running." (toward me)
• 犬が走っていきました (inu ga hashitte ikimashita) — "The dog ran off." (away from me)
• ちょっと見てきます (chotto mite kimasu) — "I'll go take a quick look." (and come back)

Time: continuing up to now, or continuing from now.

• 10年日本語を勉強してきました (juunen nihongo o benkyou shite kimashita) — "I have been studying Japanese for ten years." (right up to the present)
• これからも頑張っていきます (korekara mo ganbatte ikimasu) — "I'll keep at it from here on."
• これから寒くなっていきます (korekara samuku natte ikimasu) — "It will get colder from here." (gradual change into the future)

てくる also covers things that appear, not just things that physically move:

• 雨が降ってきました (ame ga futte kimashita) — "It started to rain." (it came on)

The intuition that ties it together: てくる means the change comes toward you or has been coming all along; ていく means it moves away or keeps going forward. If you get them backwards, the sentence still parses but the picture is wrong.

てある (te-aru): done on purpose and left that way

てある looks like ている but is not the same. It follows a transitive verb and describes a state that exists because somebody acted deliberately.

Note that the object takes が (ga), not を (wo): 窓が (mado ga). That is because てある is describing a state, not an action in progress.

ている (te-iru): worth its own article

ている is the highest-frequency auxiliary of all, and it does four separate jobs — progressive, resulting state, habitual, and experiential. 食べています (tabete imasu) can mean "I am eating" or "I have eaten", depending on the verb. That range is too much to fold into this page, so it has its own treatment.

The one thing to keep straight here: ている and てある both describe states, but ている is neutral about who caused them and てある is not.

Permission and prohibition: てもいい, てはいけない, てください

Three frozen patterns on the te-form cover most of what you need for asking, forbidding and requesting. They are worth learning as a block.

Asking permission with てもいいですか. The polite answer is いいですよ or どうぞ (douzo, "go ahead"). A refusal is usually indirect: すみません、ちょっと… (sumimasen, chotto..., "sorry, it's a bit..."). In casual speech the も drops: 撮っていい？ (totte ii?) — "Can I take one?"

Forbidding with てはいけない. This is a prohibition, not a lack of obligation. ここに入ってはいけません (koko ni haitte wa ikemasen) means "you must not enter", not "you don't have to enter". The latter is 入らなくてもいい (hairanakute mo ii). Confusing those two is a real error, not a nuance. Casually, ては contracts to ちゃ: 入っちゃだめ (haitcha dame) — "you can't go in."

Requesting with てください. This is a polite instruction, and it is fine with peers, staff and subordinates — but it is a directive, so using it to a boss or a customer sounds like an order. There, use ていただけませんか (te itadakemasen ka) or the お + masu-stem + ください pattern: お待ちください (omachi kudasai) — "Please wait."

ながら (nagara): doing two things at once

ながら attaches to the masu-stem — the form you get by removing ます — and means the two actions happen at the same time:

• 音楽を聞きながら勉強します (ongaku o kikinagara benkyou shimasu) — "I study while listening to music."
• 歩きながら話しましょう (arukinagara hanashimashou) — "Let's talk while we walk."
• テレビを見ながらご飯を食べます (terebi o minagara gohan o tabemasu) — "I eat while watching TV."

Conjugation is mechanical once you know the masu-stem: 聞く (kiku) to 聞きながら (kikinagara), 食べる (taberu) to 食べながら (tabenagara), する (suru) to しながら (shinagara), くる (kuru) to きながら (kinagara).

Two rules about ながら that the tables do not show:

The main action comes second. 歩きながら話す (arukinagara hanasu) is "talk while walking" — the talking is what the sentence is about, the walking is background. Swapping the clauses changes which action is the point.

Both clauses need the same subject. You cannot say "I studied while he listened to music" with ながら.

ながら also has a written, slightly literary use meaning "although", where the two halves are in tension rather than simultaneous:

• 知っていながら、言わなかった (shitte inagara, iwanakatta) — "Although I knew, I didn't say."
• 狭いながら、楽しい部屋です (semai nagara, tanoshii heya desu) — "It's a small room, but a pleasant one."

You meet this mostly in reading. One frozen piece of it, though, is extremely common in speech: 残念ながら (zannen nagara) — "unfortunately".

Common mistakes for English speakers

Dropping てしまう because English has no equivalent. The regret is real information. 忘れました (wasuremashita) is "I forgot"; 忘れてしまいました (wasurete shimaimashita) is "I forgot, and I feel bad about it". Leaving it out makes you sound flat.

Reading てみる as plain "do". 食べてみます is not "I'll eat", it is "I'll try it". English try is a separate verb, so your instinct is to look for one; here it is a suffix.

Mixing up ておく and てしまう. ておく is deliberate and forward-looking (予約しておく, yoyaku shite oku, "book it in advance"). てしまう is either completion or accident. 忘れておきました (wasurete okimashita) would mean you forgot on purpose — nonsense.

Reversing てくる and ていく. English "come" and "go" are speaker-anchored in a similar way, so this one usually transfers correctly — but the time uses do not. "I have been studying for ten years" needs てきました (te kimashita), never ていきました.

Mixing up てある and ている. 窓が開いています (mado ga aite imasu) is just "the window is open". 窓が開けてあります (mado ga akete arimasu) adds that someone opened it deliberately and left it. Also remember the particle changes to が.

Treating てはいけません as "don't have to". It means "must not". "Don't have to" is なくてもいい (nakute mo ii).

Putting ながら on the main action. If you mean "I listen to music while studying", the studying is the main clause: 勉強しながら音楽を聞きます (benkyou shinagara ongaku o kikimasu). Also do not confuse simultaneity with sequence: 音楽を聞いて勉強します (ongaku o kiite benkyou shimasu) means listen first, then study.

Using てください upward. It is a command with a please attached. To someone senior, soften it.

Putting it together

Auxiliaries are where a sentence stops being a word-for-word translation and starts being Japanese. They also stack onto grammar you already have: てしまう is a close relative of the passive in the way it can add a sense of being acted upon, and ながら sits in the same family as the connectives in te-mo and the four conditionals.

Romaji.live drills these as whole sentences rather than as a list, which is the only way the differences stick: 買っておきます, 食べてしまった and やってみます look similar on a table but feel completely different when you type them into a real scene. Try it in sentence practice, or paste any Japanese into the romaji converter to see how it is spelled out for typing.