O banco cobrou uma comissão bancária.

Cobrou comes from the infinitive cobrar.

Here it is in the pretérito perfeito (the simple past / preterite), 3rd person singular:

• eu cobrei = I charged
• tu cobraste = you charged
• ele/ela/você cobrou = he/she/you charged

So O banco cobrou... means The bank charged... / The bank did charge... as a completed past action.

In this sentence, cobrar means to charge, in the sense of asking for payment or taking a fee.

Common uses of cobrar include:

• cobrar uma comissão = to charge a fee/commission
• cobrar um preço = to charge a price
• cobrar uma dívida = to collect a debt

Depending on context, cobrar can also mean things like to demand, to collect, or to expect, but in this sentence to charge is the natural meaning.

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

Here, o banco means the bank. It sounds natural because we are talking about a specific bank or banking institution in the situation being described.

If you said just Banco on its own in a sentence like this, it would usually sound incomplete or unnatural.

So:

• o banco = the bank

This is very normal Portuguese usage.

No. Banco can have more than one meaning, including:

• bank = financial institution
• bench = a seat
• sometimes counter or similar meanings in certain contexts

In O banco cobrou uma comissão bancária, the meaning is clearly the financial one because of cobrou and comissão bancária.

Uma is the feminine singular indefinite article, meaning a or one.

It is used because comissão is a feminine singular noun:

• uma comissão = a commission / a fee

So the sentence is talking about a bank fee or a banking commission/charge, not a specific previously mentioned one.

Because in Portuguese every noun has grammatical gender. Comissão is a feminine noun, so it takes feminine words with it:

• uma comissão
• a comissão bancária

You usually need to learn noun gender together with the noun itself. A good habit is to learn:

• a comissão rather than just comissão

That makes agreement easier later.

Because adjectives in Portuguese usually agree with the noun they describe in gender and number.

Here:

• comissão = feminine singular
• so the adjective must also be feminine singular
• therefore: bancária

Compare:

• uma comissão bancária = a banking fee
• um serviço bancário = a banking service

So bancária changes form to match comissão.

In Portuguese, adjectives often come after the noun.

So:

• comissão bancária = banking fee / bank fee

This is the normal order here. Putting the adjective before the noun would sound unusual or change the style, and in this case it is not the natural choice.

Yes, it is very natural in European Portuguese.

In banking language, comissão is commonly used for a fee charged by the bank for a service, account maintenance, transfer, card, etc.

Related words you may also see:

• taxa = fee, rate, tax, charge, depending on context
• encargo = charge, cost, burden
• tarifa = tariff, fee, price schedule

But in a sentence about a bank charging a customer, comissão bancária is very normal.

Yes, the sentence does not explicitly say whom the bank charged. Portuguese can leave that unstated if it is obvious from context or simply not important.

So O banco cobrou uma comissão bancária just means:

• The bank charged a bank fee

If you want to say who was charged, you could add it, for example:

• O banco cobrou ao cliente uma comissão bancária.
  = The bank charged the customer a bank fee.

In everyday Portuguese, other structures are also possible, but your original sentence is perfectly complete on its own.

A useful approximation in European Portuguese is:

• comissão ≈ coh-mee-SOW̃

A few points:

• the stress is on the last syllable: -são
• ss gives an s sound, not z
• the final nasal vowel is not exactly like anything in English, so it takes practice

Also:

• banco in European Portuguese is roughly BAHN-koo, with a nasal quality in the first syllable

You do not need a perfect accent immediately, but it helps to notice that Portuguese nasal vowels are very important.

Sometimes cobrar can mean to collect, but in this sentence charged is the best choice.

Compare:

• O banco cobrou uma comissão. = The bank charged a fee.
• A empresa cobrou a dívida. = The company collected the debt.

So the best translation depends on what is being cobrado. With comissão, charged is the natural English equivalent.

Yes. It is the standard subject + verb + object order:

• O banco = subject
• cobrou = verb
• uma comissão bancária = direct object

This is the most neutral and natural way to say it.

You could change the word order in special contexts for emphasis, but for a learner this sentence is a very good model of normal Portuguese structure.