If 日本語する is not ok, why is 日本語できる ok?


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 **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)?](https://japanese.stackexchange.com/questions/22/whats-the-difference-
between-wa-%E3%81%AF-and-ga-%E3%81%8C)

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

* * *

**Summary of the question**

I agree that ジョン **が** 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 **が** 分かること **が**? 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?




> 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 `が` from 日本語** _が_ **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.




> 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 `が` from 日本語** _が_ **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.

