GRAMMAR DETAIL

ておく

do in advance; leave done

Follows the connective form of a verb to show that an action is completed ahead of time in preparation for a future situation or purpose.

Examples

旅行の前に列車の切符を買っておいた。

I bought the train tickets in advance of the trip.

会議が始まる前に、資料を机に並べておく。

I will arrange the materials on the table before the meeting begins.

Structure: Add おく to a verb's て form to express doing something in preparation for later.
Basic usage: 旅行の前に列車の切符を買っておいた。 means buying the tickets ahead of the trip.

Action and resulting state
- 資料を並べておく focuses on arranging the materials in preparation, while 資料が並べてある focuses on their resulting arranged state.
Keeping a state and contraction
- 窓を開けておく can mean opening a window and keeping it open. In conversation, 買っておく may be shortened to 買っとく.