A avaria elétrica afetou o prédio.

Because a is the feminine singular definite article, meaning the.

In A avaria elétrica:

• avaria = a feminine singular noun
• so it takes a, not o

Compare:

• a avaria = the breakdown/fault
• o prédio = the building

Portuguese articles must agree with the gender and number of the noun.

Avaria usually means a breakdown, fault, or malfunction.

In this sentence, avaria elétrica suggests:

• an electrical fault
• an electrical breakdown
• a problem in an electrical system

It is a fairly common word in technical, maintenance, and everyday contexts.

For example:

• Houve uma avaria no elevador. = There was a fault/breakdown in the lift.
• A avaria foi reparada. = The fault was repaired.

Because elétrica is an adjective describing avaria, and adjectives must agree with the noun in gender and number.

Here:

• avaria is feminine singular
• so the adjective is also feminine singular: elétrica

Other possible forms:

• elétrico = masculine singular
• elétrica = feminine singular
• elétricos = masculine plural
• elétricas = feminine plural

So:

• avaria elétrica
• but problema elétrico

In Portuguese, adjectives often come after the noun, especially when they are simply describing a type or quality.

So avaria elétrica literally follows the common Portuguese order:

• noun + adjective

This is very natural in Portuguese, even though English usually says:

• electrical fault

Portuguese can sometimes place adjectives before the noun, but that often changes the tone or meaning. In this sentence, the normal order is avaria elétrica.

Afetou is the pretérito perfeito do indicativo in Portuguese, which often corresponds to the English simple past.

It comes from the verb afetar = to affect.

Conjugation:

• eu afetei = I affected
• tu afetaste
• ele/ela/você afetou = he/she/you affected

So afetou means:

• affected
• had an effect on

In this sentence, it refers to a completed past event.

Because afetar is a direct transitive verb. It takes a direct object without a preposition.

So:

• afetar algo = to affect something

Here:

• o prédio is the direct object
• therefore no a, em, or other preposition is needed

Examples:

• A chuva afetou o trânsito. = The rain affected traffic.
• O problema afetou a escola. = The problem affected the school.

Prédio usually means building, especially a constructed urban building.

In European Portuguese, it often refers to:

• an apartment building
• a block
• a multi-storey building
• a property/building structure in general

It does not always mean exactly the same thing as English building in every context, but building is the best general translation here.

A nearby word is edifício, which is also building, but prédio is extremely common in everyday Portuguese.

Prédio is pronounced roughly like PREH-dyoo in European Portuguese, though the exact sound is different from English.

The written accent in prédio shows the stressed syllable:

• PRÉ-dio

Without the accent, the stress pattern would not be the same.

A rough breakdown:

• pré = stressed syllable
• dio = unstressed ending

European Portuguese pronunciation may sound more reduced and compressed than Brazilian Portuguese, so listening to native audio is especially helpful.

Yes, it is natural and grammatical.

It sounds like something you might see in:

• a news report
• a maintenance report
• a formal description of an incident

Depending on context, native speakers might also say things like:

• Uma avaria elétrica afetou o prédio. = An electrical fault affected the building.
• O prédio foi afetado por uma avaria elétrica. = The building was affected by an electrical fault.

Your sentence is clear, standard, and natural.

Yes. Depending on context, Portuguese speakers might use other expressions, such as:

• falha elétrica = electrical failure/fault
• problema elétrico = electrical problem
• pane elétrica = electrical breakdown, though this is less European-sounding and more associated with other varieties in some contexts

Still, avaria elétrica is a good and natural choice, especially when referring to a technical malfunction.

Almost, but not perfectly.

Word by word:

• A = the
• avaria = breakdown/fault
• elétrica = electrical
• afetou = affected
• o prédio = the building

So the structure is close to English, but English normally prefers:

• The electrical fault affected the building.

The biggest difference is that Portuguese uses noun + adjective here:

• avaria elétrica where English uses:
• electrical fault