My Japanese coworker has been unable to explain clearly this. I know that the difference comes up naturally but as someone learning Japanese I need a few examples and grammar rules to know which one to use.

Could you help me understand when to use each of them concretely?

  • Do you have an example sentence or anything? I don't think I've seen these used in similar ways, but I could be wrong.
    – ssb
    Sep 30, 2014 at 1:35
  • 2
    なるべく is an adverbial form, なるべき is an adnominal form.
    – dainichi
    Sep 30, 2014 at 4:14
  • I am led to believe those are not similar by the first comment and the second comment seems to indicate they are two forms of the same base, which makes them similar in at least one way. I do not have examples, I just remember hearing both and not being sure of how to interpret them.
    – Aki
    Sep 30, 2014 at 5:46
  • 1
    @Aki They're etymologically two forms of the same thing, but なるべく has become a word in its own right and needs its own dictionary entry, as the answers below explain. You can see this for yourself if you check a monolingual dictionary―they list it as a 副詞.
    – user1478
    Sep 30, 2014 at 6:40

2 Answers 2


「なるベく」 should be considered a single word meaning you want to do something or want something done "as [...] as possible". For example, 「お問い合わせはなるべく短めにお願いします。」 would mean "Please keep any inquiries as short as possible.".

The 「~べき」 suffix gets attached to verbs and means "should", so 「なるべき」 means "should become". For example,「なるべきようになった。」 means "It is as it should be."

So basically,「なるベく」 is used when expressing intent (when the subject is the 1st person) or making a request (when the subject is not the 1st person), whereas 「なるべき」 is used intransitively as a qualification of how things are or are supposed to be.

  • This is really clear. Thank you for your answer. I was led to believe なるべき was to be considered a single word too.
    – Aki
    Sep 30, 2014 at 5:47
  • 1
    @Aki Yeah, it is actually. What I wanted to convey is that the ~べき suffix (and it's somewhat old-fashioned predecessor ~べし) can be used after pretty much any non-passive verb, whereas the same cannot be said for the べく part of なるべく.
    – Will
    Sep 30, 2014 at 6:32

なるべく is an adverb and the meaning is "as~as possible".

なるべき is made up from a verb なる and a Japanese old auxiliary べし. The meaning of べし is 「~して当然だ。するのがよい。」 and so on. べき is a conjugation change of べし.

For example, 明日はなるべく早く起きよう。( I will wake up as early as possible tomorrow).

あなたは英語の先生になるべきだ。(You should/have to be an English teacher).


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