Salam itu mesra.

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

So where English says:

• That greeting is friendly

Malay can simply say:

• Salam itu mesra

The relationship between the subject and the description is understood without a separate word for is.

Itu usually means that, but in sentences like this it also helps mark the noun phrase clearly.

So salam itu means:

• that greeting
• the greeting (depending on context)

In natural usage, itu can make the noun feel more specific or already known to the listener.

It can feel like either one, depending on context.

Literally, itu is that, so salam itu is most directly that greeting.
But in real Malay, itu and ini are often used in ways that overlap somewhat with English the, especially when referring to something identifiable in the conversation.

So a learner should think:

• literal sense: that greeting
• practical sense in context: possibly the greeting

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

So:

• salam itu = that greeting
• buku ini = this book
• rumah itu = that house

This is a very common noun pattern in Malay.

Mesra is an adjective. It describes someone or something as:

• friendly
• warm
• cordial
• affectionate, depending on context

In Salam itu mesra, mesra is the predicate adjective describing salam itu.

Yes, it can describe more than just people.

Mesra often describes people who are warm or friendly, but it can also describe:

• a greeting
• a tone
• a manner
• an atmosphere
• a relationship

So in this sentence, it suggests the greeting is warm or friendly in character.

Yes. This is a very normal pattern:

noun phrase + adjective

Here:

• salam itu = the subject
• mesra = the description

Malay often forms simple statements this way, without any extra linking verb.

Not as the normal neutral sentence.

Salam itu mesra is the standard order for saying that the greeting is friendly.

Putting mesra first would usually sound marked, poetic, or unnatural in ordinary learning contexts. As a beginner, it is safest to keep the normal order:

• Salam itu mesra

Not always. Salam can refer to:

• a greeting
• regards
• salutations
• in some contexts, a greeting formula such as Assalamualaikum

Its exact sense depends on context. So in this sentence, salam does not have to mean only a casual hello.

Yes, Salam mesra is possible, but it would not mean exactly the same thing in structure or feel.

• Salam itu mesra = That greeting / the greeting is friendly
• Salam mesra can sound more like a friendly greeting or even a phrase/title, depending on context

So itu helps make salam a specific subject of the sentence.

It is fairly neutral and natural in tone.

None of the words are slangy, and the structure is straightforward. Depending on context, it could appear in:

• conversation
• writing
• teaching examples
• descriptive prose

The form itself is not especially formal or especially casual.

You would usually use tidak before the adjective:

• Salam itu tidak mesra = That greeting is not friendly

Use tidak with adjectives and verbs.

A useful contrast:

• bukan is usually for nouns and identification
• tidak is usually for adjectives and verbs

Since mesra is an adjective, tidak is the right choice here.