Grammar Info

N3 Lesson 1: 7/22


Must, Should , Ought to

する → べき or するべき


Verb + べき + だ
Verb + べき + Noun

する → す(る)べき


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About べき

The auxiliary verb べき, being the attributive form of べし, is a structure in Japanese that is often paired with verbs to express that something 'ought to be done'. It implies some sort of moral obligation, or that (A) is the only reasonable course of action. This comes from the kanji ()き, which carries the meaning of being something 'permissible' (indicating that any other action would not be acceptable).
べき will be paired with the plain (non-past) form of a verb, before being followed by either , or another noun.
  • そういう(こと)本人(ほんにん)()べき
    You ought to say things like that to the person themselves.
  • (きゃく)さん意見(いけん)ちゃんと()べき
    You ought to properly listen to customers' opinions.
  • ハマサキさん尊敬(そんけい)するべき(ひと)
    Hamasaki-san is someone you ought to look up to.
  • あなた(おし)えるべき(こと)これ全部(ぜんぶ)です
    Of all the things I ought to teach you, this is the last one.
べき is also sometimes translated as 'must do (A)', or 'should do (A)' but it is important to remember that it will always have the nuance of being the only 'permissible' choice, and is therefore very strong.
It is important to note that the verb appearing with べき cannot be in past tense, and you will need to use だった or でした after べき, if you would like to say that something 'ought to have been done' in the past.
  • やばいやばい、(くるま)()まりそう!高速(こうそく)()(まえ)ガソリン()ておくべきだった
    This is not good… ahhh not good, the car is about to stop! I should have filled the car up with gasoline before I got on the highway.
  • 大変(たいへん)(もう)(わけ)ございません。こちらもっと(はや)()づくべきでした
    We are very sorry. We should have noticed this earlier.
Fun Fact
In modern Japanese, there are only 18 auxiliary verbs, of which べき is not one. べし (the standard form) is considered to be a classical auxiliary verb. Due to this, べき (and べし) are often referred to as classical auxiliary verbs.
Fun Fact
The combination of する and べき is a rare grammatical exception in Japanese, in which two forms are both considered equally correct. Due to this, either するべき, or すべき may be used.
  • 結婚(けっこん)する(まえ)相手(あいて)将来(しょうらい)(はな)するべき
    Before marrying, you should talk about the future with your partner.
  • 家族(かぞく)(なに)あっても大切(たいせつ)にすべき
    You should prioritize family no matter what happens.




    I think people who want to slim down should exercise.


    You should pay taxes.


    Because we will talk about something important at tomorrow's meeting, everyone should attend.


    You should take responsibility since you are the leader.


    You should buy this bowl. It is not often that you come across such a bargain.

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べき – Grammar Discussion

Most Recent Replies (19 in total)

  • bokudake


    I also don’t see how to distinguish between ばいい, べき, …

    Because we will talk about something important at tomorrow’s meeting, everyone should attend.

    The above sounds like an obligation.
    But, during the review there was a hint “Advice”. An advice is not a moral obligation in my understanding and seeing the hint I thought すればいい would be appropriate. But べき was expected instead.

  • nekoyama


    べき is stronger, but it can still be advice. It doesn’t have to be a moral obligation. In this case it’s just practical advice based on a strong reason.

    すればいい doesn’t fit in the gap because of the following だ.

  • bokudake


    Judging by examples of べき I’ve encountered and the example sentences what you say is true.
    Why is だ not allowed after すればいい?

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