Surat itu rasmi.

A word-by-word breakdown is:

• surat = letter
• itu = that / the
• rasmi = official / formal

So the structure is roughly letter that official or the letter is official. In natural English, this is understood as The letter is official.

In Malay, demonstratives like ini (this) and itu (that) usually come after the noun.

So:

• surat itu = that letter / the letter

This is different from English, where we say that letter, not letter that.

It can often mean either, depending on context.

• surat itu can mean that letter when you are pointing out a specific one.
• It can also be translated as the letter when English naturally uses the for a known item.

Malay does not have a separate word exactly like English the, so itu often helps make the noun definite or specific.

Malay often leaves out the verb to be in simple descriptive sentences.

So:

• Surat itu rasmi. = The letter is official.

There is no need to add a word meaning is here. This is very normal in Malay.

Yes, but it is less natural in ordinary everyday speech for a simple sentence like this.

Malay does have words like adalah and ialah, but they are not used the same way as English is in every sentence.

For a basic description, Surat itu rasmi is the most natural form.

Here rasmi is functioning like the predicate adjective: it tells you something about surat itu.

So the sentence pattern is:

• Surat itu = the subject
• rasmi = what is being said about it

This is similar to English The letter is official, except Malay does not need is.

Yes. Rasmi can carry both ideas depending on context.

For example:

• surat rasmi = formal letter or official letter
• majlis rasmi = official/formal ceremony

In Surat itu rasmi, the best translation is usually The letter is official or The letter is formal, depending on the situation.

They are different structures:

• surat rasmi = an official/formal letter
  This is a noun phrase.
• Surat itu rasmi = The/That letter is official/formal
  This is a full sentence.

So:

• surat rasmi names a type of letter
• Surat itu rasmi tells you something about a specific letter

Yes. In this sentence, rasmi works like an adjective meaning official or formal.

It describes the state or quality of surat itu.

You can use tidak before rasmi:

• Surat itu tidak rasmi.

This means The letter is not official or The letter is informal.

A very useful rule is:

• tidak is used to negate adjectives and verbs
• bukan is usually used to negate nouns

Since rasmi is adjectival here, tidak is the correct choice.

Not exactly.

• Ini surat rasmi usually means This is an official letter.
• Surat itu rasmi means That/The letter is official.

So the focus changes:

• Ini surat rasmi introduces or identifies something
• Surat itu rasmi comments on a specific letter

Also notice:

• ini = this
• itu = that

Yes, but the meaning changes.

• Surat itu rasmi. = The/That letter is official.
• Surat rasmi. by itself is usually understood as official letter or could sound incomplete depending on context.

Without itu, you lose the idea of a specific known letter.

A simple pronunciation guide is:

• rasmi ≈ rahs-mee

More roughly:

• ras sounds like rahs
• mi sounds like mee

Malay pronunciation is generally quite regular, and each written vowel is usually pronounced clearly.