A adoção aconteceu hoje.

A is the feminine singular definite article, equivalent to the.

So a adoção means the adoption.

Portuguese usually uses articles more often than English, especially with nouns that are the subject of the sentence. In this sentence, it sounds natural to say A adoção aconteceu hoje rather than just Adoção aconteceu hoje.

Because adoção is a feminine noun, so it takes a, not o.

A very useful pattern is that many Portuguese nouns ending in -ção are feminine:

• a adoção
• a informação
• a situação
• a reunião is different in form, but also feminine

So once you see -ção, it is usually safe to expect a feminine noun.

It is a noun, specifically the noun form related to the verb adotar.

• adotar = to adopt
• adoção = adoption

English works the same way:

• to adopt
• adoption

So Portuguese is using the event noun adoção as the subject of the sentence.

Aconteceu is the preterite form of acontecer.

• infinitive: acontecer = to happen
• preterite, 3rd person singular: aconteceu = happened

The preterite is used for a completed event in the past. Since the sentence refers to something that took place today as a finished event, the preterite fits well.

Because the subject is singular: a adoção.

In Portuguese, the verb agrees with the subject:

• A adoção aconteceu hoje. = singular subject, singular verb
• As adoções aconteceram hoje. = plural subject, plural verb

So aconteceu matches a adoção.

Yes, acontecer is natural here. It means something like happen, take place, or occur.

Some possible alternatives are:

• A adoção ocorreu hoje. = The adoption occurred today.
• A adoção foi realizada hoje. = The adoption was carried out today.
• A adoção se concretizou hoje. = The adoption was finalized / became official today.

Among these, aconteceu is simple, common, and very natural.

Yes. Portuguese allows some flexibility in word order.

These are all possible:

• A adoção aconteceu hoje.
• Hoje a adoção aconteceu.

The version with hoje first gives a little more emphasis to today. The original version is neutral and very natural.

A good approximation in Brazilian Portuguese is:

ah-doh-SOWN

A few important points:

• the stress falls on the last syllable: -ção
• ç sounds like s
• ão is nasal, which is one of the trickier Portuguese sounds for English speakers

A more phonetic approximation is a-do-SÃW, with a nasal ending rather than a fully pronounced English ow.

They are there for pronunciation.

• ç = a soft s sound before a, o, or u
  • so ção starts with an s sound, not a k sound
• ã = a nasal a
  • you let some air pass through the nose

So ção is pronounced roughly like são, not like kao or see-on.

Because Portuguese does not need an extra helping verb here.

English often uses structures like:

• The adoption happened today
• The adoption did happen today for emphasis
• The adoption was today in some contexts

Portuguese can express the idea directly with the main verb:

• A adoção aconteceu hoje

So the tense and completion are built into aconteceu itself.

In normal Portuguese, that would sound unnatural here.

With a specific event like this, Portuguese strongly prefers the article:

• A adoção aconteceu hoje.

Leaving out the article is only common in special styles such as headlines, notes, or very compressed writing. In ordinary speech and writing, keep a.

Placing hoje at the end is a very common and neutral way to add time information in Portuguese.

Structure-wise, the sentence is:

• A adoção = subject
• aconteceu = verb
• hoje = time expression

This is a very standard pattern in Portuguese: subject + verb + time expression.

So the sentence sounds straightforward and natural.