A seguradora indenizou o terceiro.

Seguradora usually means insurance company or insurer in Brazilian Portuguese. In everyday use, it most often refers to the company, not an individual person.

So in this sentence, a seguradora is the insurance company that made the payment.

Because seguradora is a feminine noun, so it takes the feminine article a.

This is very common in Portuguese:

• a seguradora = the insurance company
• a empresa = the company

Even though English does not assign grammatical gender to nouns like this, Portuguese does, and the article has to match the noun.

Indenizou is the 3rd person singular preterite form of the verb indenizar.

That means:

• infinitive: indenizar = to compensate / to indemnify
• ele/ela/você indenizou = he/she/you compensated

The preterite is used for a completed action in the past, so indenizou tells us that the compensation happened and was completed.

Because indenizar normally takes a direct object in Portuguese.

So you say:

• indenizar alguém = to compensate someone

That is why the sentence is:

• A seguradora indenizou o terceiro.

Not:

• indenizou ao terceiro

English learners often expect a preposition because English sometimes uses different structures, but here Portuguese uses a direct object.

Here terceiro means third party, especially in an insurance or legal context.

It does not mean the third one in a simple counting sense here. In insurance language, o terceiro is a person who is not the insurer and not the insured party, but who suffered damage or is otherwise involved as a third party.

So this is specialized vocabulary.

O terceiro means the third party, referring to a specific person already identified in the context.

If you said um terceiro, it would mean a third party, more indefinite or unspecified.

Compare:

• A seguradora indenizou o terceiro. = the insurance company compensated the third party.
• A seguradora indenizou um terceiro. = the insurance company compensated a third party.

Yes. If the third party is female, you can say a terceira.

Examples:

• A seguradora indenizou a terceira.
• A seguradora indenizou o terceiro.

In some legal or formal contexts, the masculine form can sometimes be used generically, but if you know the person is female, using a terceira is natural and clear.

Not exactly.

Indenizar is more specific and is very common in legal, insurance, and damages contexts. It usually means paying compensation because of a loss, injury, or damage.

Compensar is broader and can mean:

• to compensate
• to make up for
• to offset

So in an insurance sentence, indenizar is the more precise and natural verb.

In Brazilian Portuguese, it is approximately:

in-deni-ZOW

A rough breakdown:

• in
• de
• ni
• zou with the stress on the last syllable

The ending -ou in Brazilian Portuguese often sounds like oh / oo blended together, and in this word the stressed final part is the most noticeable.

Yes. This version is the most direct and neutral:

• A seguradora indenizou o terceiro.

A passive version would be:

• O terceiro foi indenizado pela seguradora.

Both are correct, but they focus on different things:

• active voice focuses on the insurance company
• passive voice focuses on the third party

The original sentence is a very natural active-voice sentence.