A atividade econômica é importante.

A is the feminine singular definite article, meaning the.

It is used here because atividade is a feminine singular noun:

• a atividade = the activity

In Portuguese, articles are used more often than in English, including with many general or abstract nouns.

You learn the gender of each noun as part of the word. In this case, atividade is feminine, so it takes:

• a atividade
• atividade econômica

Many nouns ending in -dade are feminine:

• a cidade
• a liberdade
• a atividade

Because atividade is feminine, any adjective that agrees with it also has to be feminine.

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

Here:

• atividade = feminine singular
• so the adjective must also be feminine singular
• econômico → masculine singular
• econômica → feminine singular

So:

• o setor econômico
• a atividade econômica

Some Portuguese adjectives change form for gender, but others have the same form for masculine and feminine.

Importante is one of those adjectives:

• o trabalho importante
• a atividade importante

So even though atividade is feminine, importante stays importante.

É is the third-person singular form of the verb ser:

• eu sou
• você/ele/ela é

It means is here.

The accent is important because:

• é = is
• e = and

So the accent changes the meaning completely.

In Portuguese, adjectives often come after the noun.

So:

• atividade econômica

This is very normal and natural in Portuguese. English often puts adjectives before the noun, but Portuguese frequently puts them after.

A rough pattern here is:

• article + noun + adjective + verb + adjective

So:

• A atividade econômica é importante.

Yes. This is a very standard Portuguese sentence structure:

• A atividade econômica = subject
• é = verb
• importante = predicate adjective

So the order is:

• Subject + verb + adjective

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

The accent in econômica shows the stressed syllable.

It is stressed on NÔ:

• e-co-NÔ-mi-ca

Without getting too technical, the accent helps you know where to put the stress when speaking.

This matters because Portuguese pronunciation depends a lot on stress placement.

You would make the article, noun, verb, and changing adjective plural:

• As atividades econômicas são importantes.

Breakdown:

• a → as
• atividade → atividades
• econômica → econômicas
• é → são
• importante → importantes

This shows how agreement works across the whole sentence.

In most normal Portuguese, A atividade econômica é importante sounds more natural.

Leaving out the article is sometimes possible in special contexts, such as:

• headings
• note-taking
• very general or technical writing

But for a normal sentence, a learner should usually keep the article:

• A atividade econômica é importante.

Here, econômica means economic, not economical.

That is an important distinction for English speakers:

• atividade econômica = economic activity
• econômico/econômica can sometimes mean economical in other contexts, depending on usage

But in this sentence, the meaning is clearly economic because it describes a type of activity, not something that saves money.