～ておく
do in advance / preparatory action
～ておく is made by taking the て-form of a verb and adding おく (from 置く, “to put / to place”). It shows that you do an action now so that things will be ready later.
English usually needs an extra phrase like “in advance”, “ahead of time”, or “...so it’s ready” to express the same idea.
1. Preparing for the future
Use ～ておく when you do something as preparation for what comes next.
ビールを冷やしておく。
“I’ll chill the beer in advance.”
- ビール = beer
- を = object marker
- 冷やしておく（ひやしておく）= will chill (in advance)
旅行の前に、ホテルを予約しておきました。
“I booked a hotel before the trip.”
- 旅行（りょこう）= trip
- の前に（のまえに）= before
- ホテル = hotel
- を = object marker
- 予約しておきました（よやくしておきました）= booked (in advance)
2. Leaving things as they are
～ておく can also mean leaving a state in place on purpose, because that state will be useful later.
窓を開けておいてください。
“Please leave the window open.”
- 窓（まど）= window
- を = object marker
- 開けておいて（あけておいて）= leave (it) open
- ください = please (do)
How to form it
Verb て-form + おく
- 冷やす（ひやす）= to chill → 冷やしておく（ひやしておく）= chill in advance
- 買う（かう）= to buy → 買っておく（かっておく）= buy ahead of time
- 開ける（あける）= to open → 開けておく（あけておく）= leave open
In casual speech, ～ておく often shrinks to ～とく: 冷やしておく → 冷やしとく.
Key idea
Think of ～ておく as “putting” an action in place: you do it now, on purpose, so that the result is sitting there ready for later.
Built on the same stem
Updated .