A operação demorou oito horas.

Because a means the and points to a specific operation.

In Portuguese, it is very common to use the definite article where English also uses the:

• A operação = the operation

If you said just Operação on its own, it would usually sound incomplete in a normal sentence like this.

Demorou is the pretérito perfeito in European Portuguese, which corresponds here to the simple past in English.

It comes from the verb demorar:

• eu demorei
• tu demoraste
• ele/ela demorou
• nós demorámos
• vós demorastes
• eles/elas demoraram

So A operação demorou oito horas uses the 3rd person singular form because the subject is A operação.

Portuguese often uses demorar where English uses take for time.

So:

• A operação demorou oito horas = The operation took eight hours

This is very natural Portuguese.

A useful pattern is:

• [thing/event] + demorar + amount of time

Examples:

• O filme demorou duas horas.
• A viagem demorou três horas.

Because Portuguese does not need a preposition here.

English says:

• It took eight hours

Portuguese says:

• Demorou oito horas

The time expression oito horas works directly after the verb.

This is very common with verbs of duration such as demorar and durar.

Because the subject is A operação, not oito horas.

In this sentence:

• A operação = subject
• demorou = verb
• oito horas = expression of duration

So the verb agrees with operação, which is singular.

Yes. A operação durou oito horas is also correct and very natural.

The difference is roughly this:

• durar = to last, to have a duration
• demorar = to take time

In many contexts, both work:

• A operação demorou oito horas
• A operação durou oito horas

With demorar, there can sometimes be a slight feeling of it took that long, but in many everyday sentences the difference is small.

No. Operação can mean different kinds of operation, depending on context:

• a medical operation
• a military operation
• a business or technical operation
• a mathematical operation

In this sentence, many learners would naturally understand it as a medical operation, but the word itself is broader.

Because the most neutral Portuguese order is:

• subject + verb + time expression

So:

• A operação = subject
• demorou = verb
• oito horas = duration

This is the most straightforward and natural order for a normal statement.

You could change the order for emphasis in some contexts, but this version is the standard one.

Sometimes, but not in exactly the same way.

English often says:

• The operation took eight hours

A learner may want to translate took with levou, but Portuguese usually prefers demorou or durou here.

So the natural choices are:

• A operação demorou oito horas.
• A operação durou oito horas.

Levar is very common in other time expressions, especially with people:

• Levei duas horas a fazer isto. = It took me two hours to do this.

So levar often appears when a person is involved in doing something.

A rough European Portuguese pronunciation is:

• operação ≈ oh-puh-ruh-SOWN

A few important points:

• the final -ção is nasal
• the stress is on the last syllable: -ção
• the unstressed vowels in European Portuguese are often reduced, so it may sound less clear than in careful spelling-based pronunciation

And demorou is roughly:

• duh-moh-ROH

with the stress on the final syllable.

In normal running text, especially in learning materials, oito is usually written as a word:

• A operação demorou oito horas.

You may also see:

• A operação demorou 8 horas.

Both are understandable. Writing the number is common in many practical contexts, but writing it out is often preferred in more formal or careful prose.

You put não before the verb:

• A operação não demorou oito horas.

That means:

• The operation didn’t take eight hours.

This is the normal position for não in Portuguese:

• subject + não + verb

In European Portuguese, you can often keep the same word order and just use intonation:

• A operação demorou oito horas?

In writing, the question mark shows it clearly.

If you want a question with a question word, you could say:

• Quanto tempo demorou a operação? = How long did the operation take?

That is a very useful pattern:

• Quanto tempo demorou + noun?