ない vs 無い: Negative ある vs adjective?


How would I distinguish ない as in the negative of ある and 無い the adjective? For
example, if we have the sentence

> 食べ物がない

is the ない there just the negative form of ある or is it specifically the
i-adjective? I always assumed the former, but recently while reading an older
novel which used kanji for words that have mostly dropped them more recently,
I did see 無い used in that way, and obviously the kanji made the distinction
clear. I'd mainly find this concerning for polite speech, since there's a more
obvious difference between ありません and ないです.

Thanks!




In the Standard Japanese vocabulary, the adjective ない replaces plain negative
of ある (whose regular form should have been *あらない). It's the same phenomenon
with the past form of "go" being "went" in English, called
**[suppletion](https://en.wikipedia.org/wiki/Suppletion)**.

So the answer is: _it is both an adjective and the negative of ある_.

> _I did see 無い used in that way, and obviously the kanji made the distinction
> clear._

There's no distinction and whether they use kanji or not belongs to personal
preferences. It's however true that the older the more kanji they tend to use,
since [the post-WWII mainstream orthography has discouraged people from using
kanji for function words](https://japanese.stackexchange.com/q/24068/7810).

> _I'd mainly find this concerning for polite speech, since there's a more
> obvious difference between ありません and ないです._

This is a good point. Prescriptively this effect of suppletion only involves
its plain form and the polite negative is regular: ありません.

However in reality, we do apply it to polite form and make a phrase ないです. The
two forms are competing, and when to use which is [another somewhat delicate
problem](https://japanese.stackexchange.com/q/2574/7810).

* * *

Also see:
[「ある」と「ない」は動詞か形容詞か…](https://japanese.stackexchange.com/q/30356/7810)

