How to tell them apart
てある describes a state that already exists because someone did something earlier — the action is finished and you're observing the result, like 窓が開けてある. ておく focuses on the act of doing something now in preparation for later, like ビールを買っておいた. Swapping them is unnatural because てある won't convey the preparatory intent and ておく won't describe a visible resultant state.
- てある Use てある when you're describing a current state that results from a completed action.
- おく Use ておく when you do something now in preparation for a future need.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| てある tearu | Something is in a completed or done state | N4 |
| おく oku | Carry out an action beforehand or leave it done | N4 |
てある tearu
Something is in a completed or done state
てある attaches to the te-form of a verb and describes a state that exists because something has been done, often something done in advance or on purpose. It commonly appears with verbs like 書く or 言う to report what is written or said, and can follow かれて in passive-style uses.
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すでに言ってあるように、これもあなたの仕事のうちだ。
This is also part of your work, as I told you before.
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フランス語で書かれてあるので、この本は読むのがたいへんだ。
Written in French, this book is not easy to read.
おく oku
Carry out an action beforehand or leave it done
The auxiliary おく attaches to the te-form of a verb and shows that the action is done in advance or left in that state for a later purpose, as in 買っておく (buy ahead of time) or きれいにしておく (keep things clean). It is common in both plain and polite speech.
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父は、よく私に、物をきれいにしておくようにと言う。
Father often tells me to keep things clean.
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人を待たせたままにしておくべきではない。
You should not keep people waiting.
てある and おく are both JLPT N4 grammar points that Japanese learners often mix up. This page compares them side by side on meanings, usage and example sentences, so you can tell them apart.