O prazo máximo é de uma semana.

Not quite.

Prazo usually means a deadline, time limit, or allowed period of time to do something.

So in this sentence, prazo is not just time in a general sense. It refers to the maximum period you are given.

Compare:

• tempo = time in general
• prazo = a set period / deadline / limit

For example:

• Não tenho tempo. = I don’t have time.
• O prazo termina amanhã. = The deadline ends tomorrow.

So O prazo máximo means the maximum allowed time period.

Because prazo is a masculine singular noun.

In Portuguese, articles and adjectives usually agree with the noun in gender and number:

• o = masculine singular
• prazo = masculine singular
• máximo = masculine singular adjective

So:

• o prazo máximo
• not a prazo máxima

If the noun were feminine, the adjective would change too. For example:

• a duração máxima = the maximum duration

In Portuguese, adjectives often come after the noun.

So:

• prazo máximo = maximum deadline / maximum time limit

This is the most normal order here.

Some adjectives can go before the noun, but máximo commonly comes after it in this kind of factual or technical expression.

For example:

• velocidade máxima = maximum speed
• temperatura máxima = maximum temperature
• prazo máximo = maximum deadline / maximum time limit

Because de is commonly used in Portuguese when stating the amount, duration, or limit of something.

So é de uma semana means something like:

• is of one week
• more naturally in English: is one week / is for one week

With nouns like prazo, duração, limite, altura, peso, and so on, Portuguese often uses de before the measurement or quantity.

Examples:

• A duração é de duas horas. = The duration is two hours.
• O limite é de 30 euros. = The limit is 30 euros.
• O prazo máximo é de uma semana. = The maximum time limit is one week.

You may sometimes hear structures without de in other contexts, but here é de uma semana is the standard and natural phrasing.

It can feel like both.

In uma semana, uma is grammatically the feminine singular form of the indefinite article, but in this context it also clearly expresses the quantity one.

Because semana is feminine, you get:

• uma semana = a week / one week

In practice, English often does the same kind of double job with a:

• a week can also mean one week

So here uma semana is best understood as one week.

Because semana is a feminine noun.

In Portuguese:

• um = masculine singular
• uma = feminine singular

So:

• um prazo = a deadline / a time limit
• uma semana = a week

This is an important agreement pattern to get used to.

It may be understood, but O prazo máximo é de uma semana is more natural and standard.

Using de makes the sentence sound more idiomatic when giving a limit, duration, or measured amount.

So for learners, the safest choice is:

• O prazo máximo é de uma semana.

That is the form you should aim to produce.

If the maximum period were more than one week, you would change the quantity:

• O prazo máximo é de duas semanas. = The maximum time limit is two weeks.
• O prazo máximo é de três meses. = The maximum time limit is three months.

Notice:

• semana → semanas
• uma → duas, três, etc.

The rest of the sentence stays the same unless the noun prazo itself becomes plural:

• Os prazos máximos são de duas semanas. = The maximum deadlines are two weeks.

Yes, it is fairly neutral to formal and very common in practical contexts such as:

• business
• contracts
• applications
• deliveries
• customer service
• official instructions

It sounds natural in administrative and everyday practical Portuguese.

For example:

• O prazo máximo de entrega é de uma semana.
• O prazo máximo para responder é de 10 dias.

So it is not strange or overly technical, but it is more about procedures and limits than casual conversation.

Sometimes, but not always.

Possible related words include:

• tempo = time
• período = period
• duração = duration
• prazo = deadline / allowed period

They are not exact synonyms.

For example:

• O tempo máximo é de uma semana.
  This is possible in some contexts, but it sounds less precise.

• A duração máxima é de uma semana.
  This focuses on how long something lasts.

• O prazo máximo é de uma semana.
  This focuses on the allowed time limit or deadline.

So prazo is the best choice when talking about a permitted period to complete something.

A rough pronunciation guide is:

oo PRAH-zoo MAK-see-moo eh d(uh) OO-muh suh-MAH-nuh

A few notes for European Portuguese:

• prazo: the z sounds like z
• máximo: the x here sounds like ks
• é is a clear open eh
• de is often reduced in fast speech
• unstressed vowels are often weaker in European Portuguese than in Brazilian Portuguese

So in natural European Portuguese speech, the whole sentence may sound more reduced and compact than the spelling suggests.

Yes, very easily. This sentence pattern is very productive.

Examples:

• O prazo máximo para pagamento é de uma semana.
  = The maximum payment deadline is one week.

• O prazo máximo de entrega é de uma semana.
  = The maximum delivery time is one week.

• O prazo máximo para apresentar o documento é de uma semana.
  = The maximum time limit to submit the document is one week.

So a very useful pattern is:

O prazo máximo para/de + noun/verb idea + é de + time period