Learn Hardcore Portuguese (Portugal): A surpresa de aniversário para a Maria foi organizada em segredo. - The birthday surprise for Maria was organised in secret.

In surpresa de aniversário, the preposition de is being used in a very common way: to show the type or theme of something, not possession. It’s like saying birthday surprise in English.

surpresa de aniversário = a surprise related to a birthday / a birthday surprise
festa de aniversário = birthday party
bolo de chocolate = chocolate cake
filme de terror = horror film

If you say surpresa do aniversário (de + o), it sounds more like the surprise of the birthday, i.e. a surprise that belongs to or is part of that specific birthday that we already have in mind. It’s grammatically possible, but in this neutral sentence it feels less natural and more specific than needed.

So de aniversário is the normal choice to express the idea of a birthday-type surprise.

Why is it para a Maria and not just para Maria?

In European Portuguese, using the definite article o / a before people’s first names is very common in everyday speech, including after prepositions:

Vi a Maria ontem. – I saw Maria yesterday.
Falei com o João. – I spoke with João.
Comprei isto para a Maria. – I bought this for Maria.

So para a Maria is the default, natural form in Portugal.
Para Maria (without the article) is not wrong, but it sounds more formal, literary, or stylised, and is less typical in casual speech.

In many varieties of Brazilian Portuguese, the article before first names is much less common, which is why this may look strange if you know Brazilian usage.

Could we say para ela instead of para a Maria?

Yes, you can:

A surpresa de aniversário para ela foi organizada em segredo.

This means The birthday surprise for her was organized in secret.

The choice depends on context:

Use para a Maria when you want to specify exactly who it is for, or you’re introducing that information for the first time.
Use para ela when Maria has just been mentioned or is already obvious, so repeating the name would sound repetitive.

Both are grammatically correct; it’s mainly about clarity and style.

Why is it foi organizada and not era organizada or estava organizada?

Foi organizada uses the simple past (pretérito perfeito) passive: it describes a completed action in the past.

foi organizada = was organized (at some point, and the organizing is finished)

Era organizada (imperfeito) would describe something habitual or a characteristic, not a single event:

A surpresa de aniversário era organizada todos os anos.
The birthday surprise was (used to be) organized every year.

Estava organizada focuses on the state of being already organized at a certain moment:

Quando ela chegou, a surpresa já estava organizada.
When she arrived, the surprise was already organized.

In the original sentence, we want to report that the organizing happened as a finished event, so foi organizada is the natural choice.

Why is it organizada (feminine) and not organizado?

In Portuguese, past participles used in the passive voice behave like adjectives: they agree in gender and number with the subject.

Subject: a surpresa (feminine singular)
Participial form: organizada (feminine singular of organizado)

Compare:

A surpresa foi organizada. – feminine singular
O jantar foi organizado. – masculine singular
As surpresas foram organizadas. – feminine plural
Os eventos foram organizados. – masculine plural

So organizada matches a surpresa in gender and number.

Why is em segredo used instead of something like secretamente?

Em segredo is a very common fixed expression meaning in secret / secretly. It literally means in secrecy, but it sounds completely natural and idiomatic.

em segredo – in secret (neutral, very common)
secretamente – secretly (a bit more formal or written style)
às escondidas – on the sly, behind someone’s back (more colloquial, often with a nuance of hiding something from someone)

You could say:

A surpresa de aniversário para a Maria foi secretamente organizada.

This is grammatically correct, but em segredo is shorter, more natural, and very frequent in everyday Portuguese.

Could the sentence be in the active voice instead of foi organizada (passive)? How would that look?

Yes. The original is passive and doesn’t say who organized the surprise. To use the active voice, you need a subject (the organizers):

Os amigos da Maria organizaram a surpresa de aniversário para ela em segredo.
Maria’s friends organized the birthday surprise for her in secret.

You can also use an impersonal they in Portuguese:

Organizaram a surpresa de aniversário para a Maria em segredo.
(Literally: They organized the birthday surprise for Maria in secret.)

Another common structure in Portuguese is the se-impersonal/passive:

Organizou-se uma surpresa de aniversário para a Maria em segredo.

All of these are valid; the original passive just hides the organizers and focuses on the surprise itself.

Can para a Maria and em segredo move to other positions in the sentence?

Yes, Portuguese word order is relatively flexible, especially with phrases like para a Maria (for Maria) and em segredo (in secret). Some natural variants:

A surpresa de aniversário foi organizada em segredo para a Maria.
A surpresa de aniversário para a Maria foi, em segredo, organizada. (more formal/literary)
Em segredo, foi organizada a surpresa de aniversário para a Maria. (emphasis on it being secret)

The original:

A surpresa de aniversário para a Maria foi organizada em segredo.

is the most neutral. Moving em segredo to the beginning or the middle adds emphasis or a more literary tone, but is still correct.

Why a surpresa and not uma surpresa?

a surpresa = the surprise (definite article)
uma surpresa = a surprise (indefinite article)

Using a suggests that this surprise is specific and identifiable in the context, even if only in the speaker’s mind:

The speaker is talking about that particular birthday surprise for Maria.

If you said:

Uma surpresa de aniversário para a Maria foi organizada em segredo.

you’d be introducing the idea of such a surprise for the first time, more like a birthday surprise (some surprise or other). It’s possible, but it sounds more like you’re presenting the event as new, unknown information.

In many stories or conversations, speakers quickly move to the definite a surpresa once the event is considered specific.

Does aniversário always mean birthday, or can it be other anniversaries too?

Aniversário means anniversary in general; in everyday speech it most often means birthday, unless you specify another type:

aniversário (by itself) – usually birthday
aniversário de casamento – wedding anniversary
aniversário de morte – anniversary of someone’s death
aniversário da empresa – company anniversary

Common expressions for birthdays:

festa de aniversário / festa de anos – birthday party
surpresa de aniversário – birthday surprise
Ele faz anos amanhã. – It’s his birthday tomorrow.

So in this sentence, de aniversário is understood as birthday because that’s the default unless context says otherwise.

Do Portuguese speakers in Portugal always use an article before people’s names, like a Maria?

In European Portuguese, using the definite article with first names is very common in speech, but it’s not absolutely mandatory in all contexts.

Typical everyday usage:

A Maria chegou. – Maria arrived.
Vou ligar ao João. (= a + o João) – I’m going to call João.
Comprei isto para a Ana. – I bought this for Ana.

Situations where the article is often dropped:

In very formal or official contexts (documents, news headlines):
Maria Silva foi nomeada diretora.
In vocative (calling someone directly):
Maria, anda cá! – Maria, come here!

So a Maria in the sentence is completely natural for Portugal. In Brazil, you’ll hear the article before names much less often, depending on region and register.

Why is para used here and not por, since both can be translated as for in English?

English for can correspond to several different prepositions in Portuguese. Here’s the key difference relevant to this sentence:

para – for someone (recipient/beneficiary) or for a purpose
- Comprei flores para a Maria. – I bought flowers for Maria.
- É uma surpresa para ti. – It’s a surprise for you.
por – by, because of, in exchange for, duration, etc.
- Foi organizada pela irmã dela. – It was organized by her sister.
- Fiz isto por ti. – I did this because of you / for your sake.
- Paguei 10 euros por isto. – I paid 10 euros for this.

In A surpresa de aniversário para a Maria foi organizada em segredo, we’re talking about the recipient (who the surprise is for), so para is the correct choice.
If we wanted to say who organized it, we’d use por:

A surpresa de aniversário para a Maria foi organizada em segredo pela família.
The birthday surprise for Maria was organized in secret by the family.