From my meager understanding of Middle Japanese, I have learned that, in essence, べき is the attributive form and べし is the predicative form (feel free to correct me if I'm wrong), but in Modern Japanese, I've definitely seen evidence that contradicts this information. Can you just use whichever one you want? What are the rules?

  • 3
    For the middle Japanese (古語), what you've written is true. In modern Japanese, べし is no longer used. There are some sentences that use べし in modern Japanese (ex. 大事なことは紙に書くべし), especially in maxims or in slogans, but since it comes from middle Japanese, it keeps predicative form. Could you give us example sentences that you think contradict?
    – user51966
    Jun 29, 2015 at 10:50
  • I just meant that I saw べき used both attributively and predicatively. I guess I just saw べし used in a set phrase or something and didn't know it was maxim-only, so you've answered my question either way.
    – Kurausukun
    Jun 29, 2015 at 21:26

1 Answer 1


In modern Japanese, べし is not used except for in some fossilized expressions.

As for べき:

  1. Attributively:

べき is still used, although with a slight dated feel to it. In colloquial contexts it would often be expressed as ~ないといけない instead.

  1. Predicatively:

べき is used as a noun:

行くべきだ [sby] should go

Or you could say that べきだ is a verbal phrase. I think it makes more sense to analyze the べき without だ as copula-dropping than an actual predicative use of べき by itself.

Note that in front of the formal noun の, the noun version is used, not the attributive version

x 行くべきのだ
o 行くべきなのだ

  • <べし is not used except for in some fossilized expressions> Not necessarily. Don't you say ~すべく努力する?
    – eltonjohn
    Jul 2, 2015 at 12:28
  • 1
    @eltonjohn, well, I was talking about べし in this particular form. I didn't really touch upon 連用 usages, and I agree that べく is used productively as a slightly archaic/literary alternative for ために (or something like that). すべく in particular is definitely fossilized, since the す instead of する is archaic.
    – dainichi
    Jul 3, 2015 at 0:21

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .