置く (おく) primarily means “to put”, but when combined with another verb as a helping verb, it serves a variety of additional meanings.
As you will see in the below examples, the usages of 置く are pretty subtle and in most of the cases you can say the same things without using it. However native speakers will almost always use 置く and will make your Japanese more natural as well.
Note ～て置く becomes とく in informal conversations.
置く expresses “to keep/leave something as is”.
- この事は秘密にしておいて下さい -> Please keep this incident secret
- 猫が入れるように戸を少し開けておいた -> I left the door open a little so the cat could come in
置く expresses “to do something for someone”, especially when you are not obliged to do it.
- 犬に餌をやっといたよ -> I already fed the dog (for you)
- 洗濯物乾燥機に入れといたよ -> I put the laundry in the dryer (for you)
置く expresses “to do something in preparation, out of caution”
- 肉を汁に漬けた -> I soaked the meat in the gravy
- 肉を汁に漬けておいた -> I had the meat soaked in the gravy, marinated (to cook later)
- 宴会のためにビールを買った -> I bought beer for the party
- 宴会のためにビールを余分に買っておいた -> I bought an extra amount of beer for the party (just to be safe)
置く expresses “to get something done before a specific point of time”. Again the difference is subtle, but there will be an emphasis on “get done”.
- 死ぬ前にやりたい事 -> The things I want to do before I die
- 死ぬ前にやっておきたい事 -> The things I want to (make sure that they) get done before I die
- 会議の前に資料に目を通して下さい -> Please browse through the documents before the meeting
- 会議の前に資料に目を通しておいて下さい -> Please browse through the documents before the meeting (so that we can get right to the point)
- 心の準備をしたほうがいい -> You’d better get your mind, yourself, ready
- 心の準備をしておいたほうがいい -> You’d better have yourself ready (before the bad news comes)
- 車は明日の朝までに直します -> We will repair you car by tomorrow morning
- 車は明日の朝までに直しておきます -> We will have your car repaired and ready before tomorrow morning
- そのことは私から彼に話す -> I will talk to him about it
- そのことは私から彼に話しておく -> I will talk to him about it (so that he really understands the gravity/seriousness of it)
置く expresses “to do/assume something temporarily”
- 今日はここまでにしよう -> Let’s call it a day here
- 今日はここまでにしておこう -> Let’s call it a day here (and continue tomorrow)
- 取り敢えずは彼が正しいことにしよう
- 取り敢えずは彼が正しいことにしておこう -> More sense of temporariness
- Let’s assume for now, that he is right
事にしておく is a phrase that means “to pretend”.
- これは無かった事にしておいて下さい -> Please pretend that this didn’t happen