Gigi saya sakit malam ini.

to be

Breakdown of Gigi saya sakit malam ini.

• malam ini: tonight
• gigi: the tooth
• sakit: painful

Questions & Answers about Gigi saya sakit malam ini.

Where is the verb to be in this sentence? Why is there nothing like is?

Indonesian normally does not use a verb like to be (is/am/are) between a subject and an adjective or noun.
So:

• Gigi saya sakit literally: Teeth my painful → understood as My teeth are painful / My tooth aches.

There is no missing word; the sentence is already complete without an equivalent of is.

Is sakit a verb meaning hurt, or an adjective meaning painful / sick?

Sakit can function both ways:

• Like an adjective: Dia sakit → He/She is sick.
• Like a verb in English translation: Gigi saya sakit → My tooth/teeth hurt.

Grammatically, Indonesians usually treat sakit more like an adjective (in pain / sick), but in English we often translate it as a verb (hurt) for naturalness.

Why does the sentence start with gigi instead of saya? Could I say Saya sakit gigi malam ini instead?

The basic pattern is [body part] + [possessor] + sakit:

• Gigi saya sakit (malam ini).

You can say Saya sakit gigi, and it is correct, but the nuance changes slightly: