Karang gigi itu keras.

Malay often leaves out the verb to be when the predicate is an adjective or a noun.

So:

• Karang gigi itu keras = That tartar is hard
• literally: tartar that hard

This is completely normal in Malay. You do not need a separate word for is here.

Itu usually means that, but in real usage it can also make a noun phrase feel more specific, a bit like the in English.

So karang gigi itu can mean:

• that tartar
• or, depending on context, the tartar

Malay demonstratives normally come after the noun:

• buku itu = that book
• rumah itu = that house
• karang gigi itu = that tartar

That is the normal Malay pattern. Demonstratives such as ini and itu usually follow the noun.

Examples:

• buku ini = this book
• kereta itu = that car
• karang gigi itu = that tartar

So even though English says that tartar, Malay says something closer to tartar that.

It is normally written as two words: karang gigi.

It is a fixed expression meaning tartar or dental calculus. Even though the meaning is not fully predictable from the individual words, Malay still writes it as a phrase, not as a single combined word.

Malay noun combinations often put the main noun first and the describing noun second.

So in karang gigi, the second word gigi helps specify what kind of karang is meant. The whole phrase means tartar on the teeth / dental tartar.

This noun-first pattern is very common in Malay:

• rumah sakit = hospital
• air mata = tears
• karat besi = iron rust

So karang gigi follows a normal Malay-style order.

Because keras is the predicate adjective here.

The structure is:

• Karang gigi itu = the subject
• keras = the description about it

So the sentence pattern is basically:

• [subject] + [adjective]

This is a very common Malay sentence pattern:

• Rumah itu besar = The house is big
• Kopi ini panas = This coffee is hot
• Karang gigi itu keras = That tartar is hard

Yes. If you want the adjective to directly modify the noun, you normally use yang:

• karang gigi yang keras = hard tartar / tartar that is hard

Without yang, Karang gigi itu keras is understood as a full sentence: The tartar is hard, not just a noun phrase.

Yes, you can, but the nuance changes.

• Karang gigi itu keras = That/The tartar is hard
  specific tartar
• Karang gigi keras = Tartar is hard or Tartar is hard in texture
  more general, less specifically pointed out

So itu makes it more definite or more clearly identifiable in the context.

No. Keras has several meanings depending on context, such as:

• physically hard
• harsh
• strict
• loud or strong

But in Karang gigi itu keras, the meaning is clearly the physical one: hard.

Yes.

• Karang gigi ini keras = This tartar is hard
• Karang gigi itu keras = That tartar is hard

So ini means this, and itu means that. Both come after the noun phrase.

A simple pronunciation guide is:

kah-rang GHEE-ghee EE-too KER-ras

A few helpful notes:

• gigi has hard g sounds, like in go
• r in Malay is usually trilled or tapped lightly
• e in keras is often like the e in taken or a schwa-like sound, depending on accent

If you say each syllable clearly, you will be understood well.