Dia mengecilkan baju itu.

In Malay, dia is a third-person singular pronoun that can mean he, she, or sometimes it for a personified thing. Malay usually does not mark gender in pronouns the way English does.

So:

• Dia mengecilkan baju itu.
  could mean He made that shirt smaller or She made that shirt smaller.

You normally figure it out from context.

Not always. Baju is a general word for a piece of clothing worn on the upper body, and in some contexts it can even refer more broadly to clothes.

Depending on context, baju might be translated as:

• shirt
• top
• blouse
• clothes (in some situations)

So baju itu could be:

• that shirt
• those clothes
• that garment

English chooses the most natural word from context.

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

So:

• baju itu = that shirt / those clothes
• rumah ini = this house
• buku itu = that book

This is one of the basic word-order differences from English.

Because kecil by itself is mainly an adjective meaning small.

Examples:

• baju kecil = a small shirt
• rumah itu kecil = that house is small

But in your sentence, the meaning is not just small. It is to make something become smaller. For that, Malay uses a derived verb:

• kecil = small
• mengecil = to become smaller / shrink
• mengecilkan = to make something smaller / shrink something

So mengecilkan is the correct form because there is a direct object, baju itu.

Here, -kan helps form a causative/transitive verb. In simple terms, it often gives the idea of:

• cause something to become...
• make something...
• do something to an object

So:

• mengecil = become smaller
• mengecilkan = make something smaller

That is why mengecilkan baju itu means make that shirt smaller or shrink that shirt.

This pattern is very common in Malay.

This is because of how the meN- prefix changes shape depending on the first sound of the root.

The root is kecil.

When meN- attaches to a root beginning with k, the k usually drops, and the prefix becomes meng-. That gives:

• meN- + kecil + -kan
• meng- + ecil + -kan
• mengecilkan

So mengecilkan is the normal form.

This kind of sound change happens with many Malay verbs formed with meN-.

The difference is important:

• mengecil = to become smaller, to shrink
• mengecilkan = to make something smaller, to shrink something

So compare:

• Baju itu mengecil.
  = That shirt shrank.
  The shirt itself became smaller.

• Dia mengecilkan baju itu.
  = He/She made that shirt smaller.
  The person caused it.

A useful way to remember it:

• no object: often mengecil
• direct object present: often mengecilkan

Not necessarily. Grammatically, it says that dia caused the shirt to become smaller. Whether that was intentional or accidental depends on context.

For example, it could mean:

• they deliberately altered the shirt to make it smaller
• they washed it in a way that caused it to shrink

So the sentence focuses more on causing the result than on whether it was on purpose.

If you want to make intention clearer, Malay can add extra words for that.

Yes. The basic structure is:

• Dia = subject
• mengecilkan = verb
• baju itu = object

So the pattern is:

Subject + Verb + Object

This is very common in Malay and often matches basic English word order.

Yes. Malay uses passive forms very often.

A common passive version is:

• Baju itu dikecilkan olehnya.

This means That shirt was made smaller by him/her.

In less formal or very natural usage, Malay also often uses a passive pattern with the pronoun directly:

• Baju itu dia kecilkan.

That also means something like That shirt, he/she made smaller.

So Malay has more than one way to express the passive or passive-like idea.

Yes, it is grammatically natural. However, in real-life speech, what sounds most natural depends on the exact situation.

For example:

• if a tailor altered a shirt, mengecilkan baju itu is very natural
• if a shirt became smaller in the wash, speakers might choose a sentence that focuses on the shirt itself, such as Baju itu mengecil

So your sentence is good Malay, but context decides whether it is the most natural choice.