What form is あり?


On the road outside my daughter's nursery is painted 保育園アリ. I guess this is a
form of ある, but what's it called, and why is あり used not ある？




The old 終止形 of ある was あり. That means that you could end sentences with あり.

Nowadays, あり is to be considered as the antonym of なし.

> 保育園あり -- There is a nursery  
>  保育園なし -- There is no nursery




Just want to add to @永劫回帰's answer, which is a good one explaining the origin
of the verb form 「あり」.

_**Prose/Composition Grammar vs. Other Sets of Grammar:**_

While a sentence like 「[保育園]{ほいくえん} **が** ある。」 or 「保育園 **が** あります。」 is just
perfect if used in prose or compositions. Those contain not a single sign of
wordiness or unnaturalness in them. After all, each sentence consists only of
a couple of words.

If a Japanese-speaker (such as myself) saw a _**road sign**_ that reads
「保育園がある (or あります)」, it would sound far more weird than Japanese-learners might
imagine. It is wordy and very unnatural.

In English-speaking countries, one will see a street sign like this, right?

[![](https://i.stack.imgur.com/vdRbo.gif)](https://i.stack.imgur.com/vdRbo.gif)

But I will probably not see a sign that reads " _ **There will be bumps ahead
of you**_.", will I?

The same thing happens in Japanese. You will see a simple, two-word sign like
this one below.

[![](https://i.stack.imgur.com/P81bq.png)](https://i.stack.imgur.com/P81bq.png)

Saying 「段差があります。」 is just too unnecessarily long. The particle 「が」, too, only
helps the sign sound prose-like.

So, the sign 「保育園アリ」, in just two words, gives the drivers enough information
about how carefully they must drive in that neighborhood. If you have to read
something while driving, the shorter the better as long as the meaning is
clear.

(Another excellent example is newspaper headline grammar. Headlines will look
weird or even incorrect if one applied the prose/composition grammar.)

