A inundação estragou o chão.

A is the feminine singular definite article, meaning the.

It is used because inundação is a feminine singular noun:

• a inundação = the flood

In Portuguese, nouns normally need an article much more often than in English.

You usually learn the gender together with the noun: a inundação, not just inundação.

A useful clue is that many nouns ending in -ção are feminine:

• a inundação
• a estação
• a situação

So in this sentence, the article a matches the noun’s gender.

Inundação means flooding, inundation, or a flood. It is a correct and fairly formal word.

In everyday Portuguese, you may also hear:

• cheia = flood, especially when a river rises
• inundação = flooding/flood, often a bit more formal or technical

So A inundação estragou o chão is completely natural, but slightly more formal than a very everyday phrasing.

Estragou is the simple past form of estragar, meaning to damage, to ruin, or to spoil.

Here it is being used transitively:

• A inundação = the subject
• estragou = damaged/ruined
• o chão = the object

So the structure is:

• The flood damaged the floor/ground.

You do not need -se here because the flood is doing the damaging to something else.

Estragou is the pretérito perfeito in European Portuguese, which is often called the simple past in English explanations.

It refers to a completed action in the past:

• estragar = to damage
• ele/ela/você estragou = he/she/you damaged

In this sentence:

• A inundação estragou o chão = The flood damaged the floor/ground

The verb is singular because the subject is singular:

• A inundação = the flood = one event

So Portuguese makes the verb agree with the subject:

• singular subject → singular verb
• A inundação estragou

If the subject were plural, the verb would also change:

• As inundações estragaram o chão = The floods damaged the floor/ground

It can mean either, depending on context.

Common meanings of chão:

• floor inside a building
• ground or earth outside

So o chão could mean:

• the floor of a house or room
• the ground surface

Without more context, both are possible. If the sentence is about a house being flooded, the floor is probably the best translation.

Portuguese often uses definite articles where English may or may not use them.

So:

• o chão = the floor/the ground

The article makes the noun sound natural and complete in Portuguese. Leaving it out here would sound wrong:

• correct: estragou o chão
• not natural here: estragou chão

Yes. Danificou is also possible and means damaged.

The difference is mainly tone:

• estragou = spoiled, ruined, damaged; very common and natural
• danificou = damaged; often a bit more formal or technical

So both are correct, but estragou sounds very everyday and natural.

In European Portuguese, inundação is pronounced approximately like:

ee-noon-duh-SOWN

A few key points:

• -ção is a very common ending
• it sounds roughly like sown, but with a nasal vowel
• the stress is on the last syllable: -ÇÃO

That nasal ending -ão is very important in Portuguese pronunciation.

In European Portuguese, chão sounds approximately like:

shown
but with a nasal ending, not a fully English n sound.

Key points:

• ch in Portuguese sounds like English sh
• ão is nasal
• the whole word is one syllable

So it is roughly shãw, with nasal resonance.

The normal word order is:

• subject + verb + object
• A inundação estragou o chão

That is the most neutral and natural order.

Portuguese can sometimes change word order for emphasis, but in ordinary usage this sentence is best as it is.

Yes, absolutely.

Because inundação can refer to the event of flooding, not just a flood as a countable thing, good translations include:

• The flood damaged the floor.
• The flooding ruined the floor.

The best English version depends on context, but the Portuguese sentence itself is straightforward and natural.