kore ha himitu desu.

Because when は is used as the topic particle, it is pronounced wa, not ha.

So in これは秘密です, you read it as:

kore wa himitsu desu

But when は is part of a word, it is usually pronounced ha.

This is a very common thing in Japanese, and learners just have to memorize it:

• は as a particle → wa
• は inside regular words → usually ha

これ means this.

It refers to something close to the speaker, either physically or in the conversation.

Examples:

• これ = this
• それ = that (near the listener / something just mentioned)
• あれ = that over there

So in this sentence, これ is the thing being talked about: this.

は marks the topic of the sentence.

So これは means something like:

• as for this,
• speaking of this,

Then the rest of the sentence says something about that topic:

• これは = as for this
• 秘密です = it is a secret

A natural way to understand the structure is:

As for this, it is a secret.

This is not always translated literally into English, but it helps explain how Japanese sentences are built.

秘密 means secret, and it is read himitsu.

Breakdown:

• 秘 = hi
• 密 = mitsu

So:

• 秘密 → himitsu

In this sentence, it functions like a noun: a secret / secret information / something confidential.

です is often taught as is / am / are, and that is helpful at the beginner level, but it is not exactly the same as the English verb to be.

In this sentence, です makes the sentence:

• polite
• complete
• statement-like

So 秘密です means something like:

• is a secret
• it is a secret

A useful beginner understanding is:

• noun + です = polite statement

Examples:

• 学生です = (I am / he is / she is) a student
• 日本人です = (I am / he is / she is) Japanese
• 秘密です = (it is) a secret

Japanese normally does not use articles like a, an, or the.

So 秘密 can mean:

• a secret
• the secret
• just secret

The exact meaning depends on context.

That means これは秘密です could be understood in English as:

• This is a secret.
• This is the secret.

Usually, context tells you which one sounds right.

Japanese and English organize sentences differently.

English:

• This is a secret.

Japanese:

• This
  • topic marker
    • secret
      • polite ending

So:

• これ = this
• は = topic marker
• 秘密 = secret
• です = polite sentence ending / copula-like element

Japanese often puts the main descriptive part before the final verb or sentence-ending element. That is why です comes at the end.

Yes. これは秘密だ is the less formal / plain version.

Compare:

• これは秘密です。 = polite
• これは秘密だ。 = plain, casual, firmer

You would usually use です in normal polite conversation, with people you do not know well, in class, at work, and so on.

You might hear だ in:

• casual speech
• anime
• manga
• narration
• speech between close friends, depending on style

So for a beginner, です is usually the safer choice.

Yes, it is a natural and correct sentence.

It sounds like a straightforward polite statement: This is a secret.

Depending on context, Japanese speakers might also say things like:

• 内緒です。 = It’s a secret.
• 秘密だよ。 = It’s a secret.
• これは内緒です。 = This is a secret / Keep this private.

But これは秘密です is perfectly normal and easy for learners to understand.

Yes, これが秘密です is also possible, but it has a different nuance.

• これは秘密です = As for this, it is a secret.
• これが秘密です = This is the secret / This is what is secret

Very roughly:

• は presents the topic
• が identifies or emphasizes the subject

So if you are just making a general statement about this, は is very natural.

If you are answering a question like Which one is the secret?, then が may sound more appropriate:

• これが秘密です。 = This is the secret.

This is a big grammar topic, but that is the basic idea.

In normal Japanese writing, there are usually no spaces:

これは秘密です。

Spaces are often added in textbooks or beginner materials to make the sentence easier to read and to show the parts clearly.

So both represent the same sentence, but:

• これは秘密です。 = normal Japanese writing
• これ　は　秘密　です。 = learner-friendly spacing

It is read:

kore wa himitsu desu

A simple pronunciation guide:

• ko-re
• wa
• hi-mi-tsu
• de-su

A few helpful notes:

• r in Japanese is not exactly English r; it is closer to a light tap.
• u in desu is often very weak in normal speech, so desu may sound a bit like dess.
• Even so, learners should still remember the full form as desu.

Yes. Japanese often omits things that are clear from context.

For example, if everyone already knows what this is, a speaker might simply say:

秘密です。
= It’s a secret.

The subject or topic does not always need to be said explicitly.

That is very common in Japanese. Full sentences like これは秘密です are especially useful for learning grammar clearly, but real conversation often leaves out information that both speakers already understand.