الحساب آمن.

A careful MSA pronunciation is:

al-ḥisābu ʾāmin(un)

A few helpful notes:

• ح in الحساب is a deep h sound from the throat, not the ordinary English h.
• ا in حساب gives a long aa sound: ḥi-saab.
• آ in آمن is pronounced ʾā, so the word begins with a hamza plus a long aa sound.
• In normal pause at the end of the sentence, learners often hear something close to al-ḥisāb ʾāmin.

ال is the Arabic definite article, equivalent to the.

So:

• حساب = an account / account
• الحساب = the account

Also, in الحساب, the l in ال is pronounced clearly because ح is a moon letter. That means you say al-ḥisāb, not something like aḥ-ḥisāb.

In Arabic, the present-tense verb to be is usually omitted.

So Arabic often says:

• الحساب آمن
  literally: the account secure

But the natural English meaning is The account is secure.

This kind of sentence is called a nominal sentence in Arabic.

If you want past tense, Arabic normally uses كان:

• كان الحساب آمناً = The account was secure.

Because this sentence is built as:

• الحساب = the subject
• آمن = the predicate

In Arabic nominal sentences, the usual order is:

subject + predicate

So:

• الحساب آمن = The account is secure.

This is not the same as English word order with is in the middle. Arabic simply places the description after the subject.

Because آمن here is the predicate of the sentence, not an adjective inside a noun phrase.

Compare these:

• الحساب آمن = The account is secure.
• الحساب الآمن = the secure account

That difference is very important:

• without ال on آمن: a full sentence
• with ال on آمن: a noun phrase

So الحساب آمن is correct for The account is secure.

Yes, آمن is an adjective in meaning, but in this sentence it is functioning as the predicate (خبر) of the sentence.

So you can think of it in two ways:

• as a word: an adjective meaning safe/secure
• in this sentence: the predicate describing الحساب

That is why it behaves a little differently from an ordinary adjective inside a phrase like الحساب الآمن.

آمن agrees with الحساب in gender and number.

Here:

• الحساب is masculine singular
• so the predicate is آمن = masculine singular

If the noun changed, the form would change too. For example:

• الكلمة آمنة = The word is secure/safe.
  feminine singular
• الحسابات آمنة = The accounts are secure.
  non-human plural usually takes feminine singular agreement in MSA

So agreement matters.

In fully vowelled formal Arabic, the sentence is:

الحسابُ آمنٌ

Both words are in the nominative:

• الحسابُ = subject (مبتدأ)
• آمنٌ = predicate (خبر)

In everyday writing, these short vowels are usually not written, so you normally see:

الحساب آمن

And in actual speech, learners often will not hear every case ending clearly, especially at the end of a sentence.

These look similar, but they mean different things:

• الحساب آمن = The account is secure.
  full sentence

• الحساب الآمن = the secure account
  definite noun phrase

• حساب آمن = a secure account / secure account
  indefinite noun phrase

A very common learner mistake is to confuse the sentence الحساب آمن with the phrase الحساب الآمن.

Not always. الحساب can have several meanings depending on context, such as:

• account
• calculation
• arithmetic
• reckoning

But in modern tech or security contexts, الحساب very often means account, as in a user account.

So the exact meaning comes from context, even though the grammar of the sentence stays the same.