6

This is my understanding:

  1. する名詞:

    運転する。
    残業する。
    勉強する。

  2. their potential forms:

    運転することができる。
    残業することができる。
    勉強することができる。

  3. abbreviated potential forms:

    運転できる。
    残業できる。
    勉強できる。

Can you say 日本語する?
If the answer is no, how can 日本語できる be grammatically correct?
Without realizing it, you are actually saying 日本語が分かることができます.

If ジョン日本語できる is grammatically incorrect, why is it listed as the premier example of how to use with the exhaustive listing meaning in this thread with 83 up-votes: What's the difference between wa (は) and ga (が)?

I read ジョン日本語できる as ジョン日本語分かることできる. But, now it looks like a sentence with 3 that has 2 implied. That seems kind of deceptive and not that useful.


Summary of the question

I agree that ジョン日本語できる sounds ok. It looks like a sentence with one が. But, you can only create that by tacitly implying 分かること? 日本語 is not a サ変名詞. You can't say 日本語する. So, you can't simply say 日本語できる? There must be implied が?

83 up-votes cannot be wrong, so where am I wrong?

15

Can you say "日本語する"?

I suppose you can use it idiomatically or somewhat playfully (perhaps akin to something like "I'm Japanese-ing it up"), but it's not a real verb that is used.

If the answer is no, how can "日本語できる" be grammatically correct? Without realizing it, you are actually saying "日本語が分かることができます。".

日本語できる is really just dropping the from 日本語できる. Whether or not simply leaving out particles in casual speech is grammatically correct or not is debatable (I would say it isn't). Also, 分かる is a bit special in that it already includes potentiality in its own definition -- "can understand" -- so saying 日本語が分かることができます is redundant at best.

So to answer the question, 日本語できる is acceptable because it's just particle-less casual speech, while 日本語する is something that is at best not used, and completely incorrect at worst.

If "ジョンが日本語できる" is grammatically incorrect, why is it listed as the premier example of how to use が with the exhaustive listing meaning in this thread with 83 up-votes:
What's the difference between wa (は) and ga (が)?

I suspect that due to the whole point of that thread being comparing and contrasting は and が, the author of that post intentionally left out the が between 日本語 and できる to avoid further confusion about が; but I'm no mind-reader.

  • I'm saying (1) "日本語が分かる" is perfect. If "日本語できる" is derived from "日本語が分かることができる" then "日本語できる" is also perfect / formal. (2) BUT, if "日本語できる" is derived from "日本語する", then "日本語できる" also sounds goofy / informal? To me, "日本語できる" sounded inappropriate for a grammatical discussion. btw: another example sentence in that wa/ga thread, "「だれが日本語を知っていますか?」" sounds strange (wrong?). I'm sure one should say "日本語が理解できる" or "日本語が分かる". "日本語を知る" sounds like a beginner mistake. But what do i know. I can't even pass JLPT2... – david Aug 25 '15 at 20:07
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    @David_W Why do you say 日本語できる is derived from 日本語する? できる and する are different verbs. – Blavius Aug 25 '15 at 20:10
  • @Blavius "できる" is potential form of "する". Ok, so the only way you can place する next to a noun is if the noun is サ変名詞。So, how to make "日本語 + できる"? The catch-all サ変名詞 is "こと". Long story short, you place サ変名詞 into their potential forms like "残業することができる". Drop "することが" and that allows for "残業できる". Ok. So: "日本語" is a noun, but not a サ変名詞。So, how to place "できる" next to "日本語"? Only option is to attach "日本語が分かる" to the catch-all サ変名詞,"こと". This leaves "日本語が分かることをする。". Change to potential form as such: "日本語が分かることができる". Drop "が分かることが", which leaves "日本語できる". – david Aug 25 '15 at 20:25

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