〜ておく

〜ておく expresses doing something in advance as preparation for the future: 予約しておく (book ahead), 買っておく (buy in advance). The speaker does the action now, knowing it will be needed later.

〜ておく also means "leave things as they are": 窓を開けておいてください (open the window and leave it that way). Distinguish it from 〜てある: 〜ておく is about the act of preparing, while 〜てある is about the state remaining after the preparation — ホテルを予約しておきます (I'll book ahead) differs from ホテルは予約してあります (the hotel has already been booked).

In spoken language, 〜ておく often contracts to 〜とく: 買っておく → 買っとく, 調べておいて → 調べといて. You'll hear this contracted form a lot in casual conversation.

Examples

• 旅行(りょこう)の前(まえ)に、ホテルを予約(よやく)しておきます。

  Before the trip, I'll book the hotel in advance.

• パーティーの飲(の)み物(もの)を買(か)っておきましょう。

  Let's buy the drinks for the party ahead of time.

• 窓(まど)を開(あ)けておいてください。

  Please open the window and leave it open.

Related patterns

• 〜てある
• 〜てしまう
• 普通体の会話