A investigação confirmou o erro.

Portuguese often uses the definite article more than English does. In A investigação confirmou o erro, a investigação means the investigation.

If you removed the article and said just Investigação, it would usually sound incomplete or unnatural in this sentence. The speaker is referring to a specific investigation, so a is needed.

• a investigação = the investigation
• uma investigação = an investigation

So this sentence is talking about a particular investigation, not just any investigation.

Erro is a masculine singular noun in Portuguese, so it takes the masculine singular definite article o.

• o erro = the error / the mistake

This is something learners simply have to remember with the noun:

• erro → masculine
• singular → o erro
• plural → os erros

Confirmou is the pretérito perfeito do indicativo of the verb confirmar.

In this sentence, it means that the action was completed in the past:

• confirmar = to confirm
• ele/ela/você confirmou = he/she/you confirmed

So A investigação confirmou o erro means the investigation confirmed the error, as a finished event.

Because confirmar is an -ar verb, and in the pretérito perfeito the ele/ela/você form usually ends in -ou.

For example:

• falar → falou
• estudar → estudou
• confirmar → confirmou

Here, the subject is A investigação, which is a singular third-person noun, so the verb must be in the ele/ela form: confirmou.

The subject is A investigação, which is singular:

• a investigação = the investigation

Since the subject is singular, the verb must also be singular:

• A investigação confirmou
• not A investigação confirmaram

Portuguese verbs agree with the subject in number and person, just like in English:

• The investigation confirmed
• not The investigation confirmeds or The investigation confirm

Yes, it is very close in meaning and is a useful cognate.

• investigação = investigation, inquiry, examination

But as with many cognates, the exact meaning depends on context. It can refer to:

• a police investigation
• a formal inquiry
• research/investigative work in some contexts

In this sentence, A investigação confirmou o erro, it most naturally means the investigation in the sense of an inquiry or examination that established that there was an error.

Yes. In many contexts, erro can be translated as either error or mistake.

Examples:

• Houve um erro no relatório. = There was an error in the report.
• Foi um erro meu. = It was my mistake.

In your sentence, o erro could be translated as:

• the error
• the mistake

The best choice depends on the wider context.

This is the normal Portuguese word order:

Subject + Verb + Object

• A investigação = subject
• confirmou = verb
• o erro = direct object

This is very similar to English:

• The investigation confirmed the error.

Portuguese can sometimes change word order for style, emphasis, or literary effect, but this sentence uses the most neutral and standard order.

In European Portuguese, investigação is pronounced approximately like:

in-ves-ti-ga-SÃO

A few useful points:

• the final -ção sounds roughly like são
• the ão sound is nasal, which is important in Portuguese
• the stress falls on the final syllable: -ção

A rough learner-friendly approximation is:

• investigass-OW̃

But it is best to listen to native European Portuguese audio, because nasal vowels are hard to capture in English spelling.

In European Portuguese, confirmou is pronounced approximately like:

con-fir-MOU

The stress is on the last syllable:

• con-fir-MOU

The ou in European Portuguese is usually a closed sound, roughly like oh. Depending on accent and speed, unstressed vowels may sound weaker than an English speaker expects.

That would change the meaning.

• A investigação confirmou o erro = The investigation confirmed the error.
  A completed past action.

• A investigação tem confirmado o erro = The investigation has been confirming the error / has confirmed the error repeatedly or over a period.
  This suggests an ongoing or repeated process, which is much less natural in many contexts.

So for a single completed finding, confirmou is the normal choice.

Possibly, depending on context, but investigação in European Portuguese more often means investigation or inquiry than research in a general academic sense.

For academic research, Portuguese often uses:

• investigação in Portugal, especially in formal or academic language
• pesquisa much less in Portugal than in Brazil for this meaning

So in Portugal, investigação can sometimes mean research, but in this sentence the most natural reading is still the investigation.

Yes: both nouns have grammatical gender, but their gender does not have to match English patterns.

• a investigação → feminine
• o erro → masculine

This affects the articles:

• a for feminine singular
• o for masculine singular

It does not mean the investigation is “female” or the error is “male.” It is just a grammatical feature of the nouns.