Learn Hardcore Japanese: situmon ga hitotu arimasu.

Japanese often omits subjects when they’re clear from context. In 質問が一つあります (shitsumon ga hitotsu arimasu), the grammatical subject is 質問 “question,” marked by が. The speaker (I) is implied: “There is one question (that I have).” Adding 私(は) is possible but usually unnecessary unless you need contrast or emphasis: 私は質問が一つあります.

Why is が used instead of は?

が marks the grammatical subject and often introduces new information or existence. With あります, が is the default: 質問が一つあります “There is one question.”
Using は changes the nuance to a topical/contrastive frame: 質問は一つあります “As for questions, there is one (as opposed to none or more).” It can sound contrastive or explanatory depending on context.

Why あります and not います?

Use います for living/animate things (people, animals). Use あります for inanimate/abstract things. A question (質問) is inanimate, so あります is correct.

Can I say 一つの質問があります?

It’s grammatically correct and understandable, but native style prefers 質問が一つあります. Putting the counter after the noun (Noun + が + Counter + あります) is the most natural pattern for “I have X [count].” Use 一つの質問 when the number modifies the noun attributively in a larger noun phrase (e.g., 一つの質問に答える “answer one question”).

Could I say “I have” with 持つ: 質問を持っています?

That sounds unnatural. 持つ is for physically holding/possessing tangible items. For having/there being intangible things like questions, plans, time, etc., use ある／あります: 質問があります or 質問が一つあります.

Is “one” necessary? What’s the difference between 質問があります and 質問が一つあります?

質問があります = “I have a question” (or “I have questions”), with the number unspecified; usually interpreted as “a question” in context.
質問が一つあります = “I have one question,” explicitly one.
To emphasize “only one,” say 質問が一つだけあります.

Can I use other counters like 個 or 問?

The generic counter つ (as in 一つ) is natural and safe in most situations.
個 (e.g., 一個) is colloquial for physical items; for “questions” it sounds off in careful speech.
問 is a specific counter for questions/problems in tests or surveys: 一問. In such contexts, 質問が一問あります is fine and more formal/precise.

Is 一つ質問があります also correct, or must the number come after 質問?

Both work:

質問が一つあります (most common/existential pattern).
一つ質問があります places slight emphasis on the quantity first (“There’s one question I have”).
Both are natural; choose based on flow/emphasis.

How would I ask “Do you have any questions?” to an audience?

Common options:

質問はありますか？ (neutral, invites any questions)
何か質問はありますか？ (explicitly “any”)
More formal: ご質問はございますか？
Using は here frames “questions” as the topic you’re asking about; it’s the conventional choice.

How do I say “I don’t have any questions”?

質問はありません。 (most natural; は with a negative emphasizes “none.”)
質問がありません。 (grammatical but less common than the version with は in this meaning.)
Casual: 質問ないです／質問ない.

What’s the difference between あります and ございます, and when can I use ご質問?

ございます is the more formal/polite equivalent of あります for inanimate things: 質問がございます (very polite).
ご質問 adds an honorific prefix and is typically used when referring to the listener’s questions: ご質問があればお知らせください.
Talking about your own question, stick with 質問 (not ご質問): 質問が一つあります. In customer-facing/formal announcements, you’ll see ご質問 to respect the audience.

Why are there spaces between the words? Do native texts write it like that?

Standard Japanese writing doesn’t put spaces between words. The spaced version (質問　が　一つ　あります。) is a learner aid. In normal writing you’d see 質問が一つあります。

How do I read each word? Is 一つ written with kanji or hiragana?

質問 (しつもん shitsumon)
が (particle “ga”)
一つ (ひとつ hitotsu) — often written in hiragana as ひとつ; numerals like １つ also appear. All are acceptable; hiragana is common for the つ-series counters.
あります (arimasu)

How do I change the form (casual, past, negative)?

Casual present: 質問が一つある。
Polite past: 質問が一つありました。
Polite negative: 質問はありません。／質問が一つもありません。
Casual softener: 質問が一つあるんですが… (leads into a question politely).

What’s the difference between 質問 and 問題?

質問: a question you ask someone (an inquiry).
問題: a problem/task/exercise, or an issue/trouble.
So “I have one question (to ask)” = 質問が一つあります; “There’s one problem” (e.g., in a worksheet) = 問題が一つあります or “There is one issue” depending on context.

If I want to ask for permission, should I still use あります?

To request permission more directly, use a verb like “ask”:

質問してもいいですか？ “May I ask a question?”
一つ質問してもいいですか？ “May I ask one question?”
Polite: 質問よろしいでしょうか。／一つお伺いしてもよろしいでしょうか。