What form is あり?

Question

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？

Answer 1

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

Answer 2

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?

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.

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.)

Answer 3

“あり” is a 終止形 of “ある,” the same as “なし” and “ない” as mentioned by 永劫回帰. It can be compared with the English pair of words “Yes (we have)” and “No (we don’t have)”.

The 漢語 version of “あり・なし” is “有・無”, both of which are commonly used.

Here are some examples:

• 雀斑【そばかす】あり – having freckles

• 欠点【けってん】あり（の商品） – (a product) with a flaw

• 曰【いわく】あり – have something with a secret behind

• 異議【いぎ】あり!　– I have an objection. / Objection! Opposite: 異議なし!

• 勝負【しょうぶ】あり – The game is set. / Opposite: 勝負なし

• 後車{こうしゃ}あり - There's a car following us. / Opposite: 後車なし.

• 注意【ちゅうい】！道路【どうろ】に陥没【かんぼつ】あり – Attention! There is a hole in the pavement.

• 理由【りゆう】の有無【うむ】を問わず – regardless (presence or non-presence) of reasons.

• 存在【そんざい】の有無【うむ】 – presence or non-presence

• 出欠【しゅっけつ】の有無【うむ】（可否【かひ】）をお知らせください – Please let us know if you can attend or not.