kyoka ga hituyou desu.

It is read:

• 許可 = きょか
• が = が
• 必要 = ひつよう
• です = です

So the whole sentence is:

きょか が ひつよう です
Romanized: kyoka ga hitsuyou desu

A very natural pronunciation in connected speech is close to kyoka ga hitsuyou desu.

Normally, Japanese is not written with spaces like this.

A native-style version would usually be:

許可が必要です。

The spaces are often added in teaching materials to help beginners see the parts more clearly:

• 許可
• が
• 必要
• です

So the spaces are just a learning aid, not standard Japanese writing.

In this pattern, が marks the thing that is necessary.

Japanese often uses the structure:

X が 必要です
= X is necessary / X is needed

So here:

• 許可 = permission
• が = marks what is needed
• 必要です = is necessary

This is a very common pattern in Japanese.

Because 必要です is not a verb like English need.

In English, you say need permission, where need is a verb.
That makes English learners expect を.

But in Japanese, 必要 is a noun / な-adjective-type word, not a normal action verb. So Japanese uses:

許可が必要です

not

許可を必要です ❌

If you use the more formal verb-like expression 必要とする, then を can appear:

• 許可を必要とする = to require permission

But for the basic sentence pattern, use:

X が 必要です

必要 is usually treated as a な-adjective and also as a noun-like word.

That means it can be used in a few different ways:

• 必要です = is necessary
• 必要な許可 = necessary permission
• 必要があります = there is a need

In your sentence, 必要 is being used as the main predicate of the sentence, followed by です for politeness:

許可が必要です

So you do not say 必要なです here.

です makes the sentence polite.

Compare:

• 許可が必要です = polite
• 許可が必要だ = plain
• 許可が必要 = casual / less complete-sounding in some contexts

So です is there because this is the normal polite form you would use in many everyday situations, signs, notices, or formal speech.

Japanese often leaves out the subject when it is obvious from context or when the sentence is meant to be general.

So 許可が必要です could mean different things depending on the situation, such as:

• Permission is required
• You need permission
• We need permission
• A permit is necessary

Japanese often prefers this kind of context-based expression instead of always stating the subject explicitly.

Yes, but the nuance changes.

• 許可が必要です = neutral statement: permission is required
• 許可は必要です = as for permission, it is necessary

Using は can sound more contrastive or topical, as if you are focusing on permission specifically, maybe compared with something else.

For example, if someone asks whether money is needed or not, you might say:

• お金は要りませんが、許可は必要です。
  Money is not needed, but permission is.

So が is the most neutral default choice here.

Yes. It is very natural.

許可が必要です is a normal and useful phrase in:

• rules
• notices
• workplaces
• schools
• buildings
• official instructions

It has a slightly formal, matter-of-fact tone, which fits signs and notices well.

You may also see longer versions such as:

• 事前に許可が必要です。 = Prior permission is required.
• 入室には許可が必要です。 = Permission is required to enter the room.
• 撮影には許可が必要です。 = Permission is required for photography.

Yes, you can.

Both are correct:

• 許可が必要です
• 許可が要ります

The difference is mainly nuance:

• 必要です sounds a bit more formal, objective, or written
• 要ります sounds a bit more conversational and verb-like

So in many official or written contexts, 許可が必要です is especially common.

Yes. Depending on context, 許可 can refer to:

• permission in general
• approval
• authorization
• a permit

So 許可が必要です may sometimes be understood as:

• permission is required
• authorization is required
• a permit is required

The exact English wording depends on the situation.

Because な is only used when the adjective comes before a noun.

For example:

• 必要な書類 = necessary documents
• 必要な許可 = necessary permission

But when 必要 is the main predicate of the sentence, you do not use な:

• 許可が必要です ✅
• 許可が必要なです ❌

So:

• before a noun: 必要な + noun
• at the end of a sentence: 必要です / 必要だ

Yes. It is a complete sentence.

Japanese does not always need an explicit subject, and 必要です works as the predicate. So even though it may feel shorter than an English sentence, it is fully natural and complete.

Structure:

• 許可 = permission
• が = marks what is needed
• 必要です = is necessary

That is enough to make a full sentence in Japanese.