Most languages do well without articles. In this sense, English and Romance languages like Portuguese belong to a minority.

The Portuguese definite articles – o, a, os, as – are the equivalent of the in English and we use them to designate specific nouns.

The Portuguese indefinite articles on the other hand – um, uma, uns, umas – correspond to the English article a/an; we use them to introduce and designate non-specific nouns.

Read on.

Definite articles

Portuguese definite articles are the equivalent of the in English. We use them to designate specific nouns with which they agree in gender and number: 

	♀	♂
singular	a (a flor)	o (o jardim)
plural	as (as flores)	os (os jardins)

Usage of the definite article

In general, definite articles designate specific things and living beings:

Eu não gosto muito de gatos, mas o teu gato é simplesmente irresistível. I am not so fond of cats, but your cat is simply irresistible.

! One difference between European and Brazilian Portuguese is that the latter standard often skips definite articles. Learn more about how these two standards of Portuguese compare: European vs. Brazilian Portuguese – How Different Are They Really?

With people’s names

As a rule of thumb, we use the definite article when referring to people:

Ontem vi a Joana. Yesterday, I saw Joana. O Pedro pareceu-me um pouco triste. Pedro looked a bit sad.

Also with titles and formal forms of address:

A senhora sente-se bem? Do you feel alright? O Sr.* Silva vai querer um café? Would Mr. Silva like a cup of coffee?

* Sr. is short for Senhor and corresponds to Mr. in English.

Continents and countries

In general, we use the definite article when mentioning continents and countries:

A Europa pode ser vista como uma península asiática. Europe can be seen as an Asiatic peninsula.  A Suécia tem muitos lagos. Sweden has many lakes. O Brasil é o país com mais falantes nativos de Português. Brazil is the country with the highest number of Portuguese native speakers.

There are, however, a few exceptions. For instance, we don’t use the definite article with countries like Portugal, Angola, or Moçambique:

Portugal fica na Europa. Portugal is in Europe.

Concerning countries such as Inglaterra, França, or Itália, the use of the definite article is optional. 

A França tem vinhos de qualidade. = França tem vinhos de qualidade. There are quality wines in France.

Days of the week

We use definite articles to refer to the days of the week:

O meu dia preferido é o sábado. My favorite day is Saturday.

Possessive pronouns and adjectives

Normally, possessive pronouns and adjectives are preceded by a definite article:

Comprei o meu carro em segunda mão. I bought my car secondhand.

Reading tips: Learn more about Portuguese possessives: Portuguese Possessive Pronouns and Adjectives.

Omission of the definite article

Well-known people

We often leave out the definite article when referring to well-known people and public figures:

Luís de Camões é um símbolo nacional. Luís de Camões is a national symbol.

Vocatives

We don’t use definite articles when we say someone’s name to call their attention (vocatives):

Pedro, queres tomar um chá? Pedro, do you want some tea?

Cities and towns

In general, we leave out the definite article when referring to cities:

Aveiro é uma cidade universitária. Aveiro has a university. Paris é uma cidade cara. Paris is an expensive city.

There are a few exceptions like the city of Porto or Rio de Janeiro:

O Porto fica no norte de Portugal. Porto is in the north of Portugal.

After certain verbs 

We don’t use the definite article in association with a few verbs such as Estudar, Falar, or Tocar:

Ela estuda Biologia.  She studies biology. Tocas guitarra? Do you play the guitar?

Generalizations

We often leave out the definite article when making generalizations:

Adoro fazer desporto. I love doing sports.

Contractions of the definite article

Here are the contractions between the definite articles and the prepositions em, de, a, and, por:

	a	o	as	os
em	na	no	nas	nos
de	da	do	das	dos
a	à	ao	às	aos
por	pela	pelo	pelas	pelos

Learn more about Portuguese prepositions: Basic Portuguese Prepositions and Contractions: An Inclusive Usage Rundown.

Indefinite articles

Portuguese indefinite articles correspond to the English forms a, an, and some. 

We use them to introduce and designate non-specific nouns with which they agree in gender and number: 

	♀	♂
singular	uma	um
plural	umas	uns

Usage of the indefinite article

In general, we use indefinite articles to designate non-specific things and living beings:

Ontem encontrei-me com um amigo meu. Yesterday I met a friend of mine.

If we specify which friend, we then use the definite article:

Ontem encontrei-me com o Luís. Yesterday I met Luís.

Note! Although umas/uns are plural forms of the indefinite article, in practice we don’t use them to designate plural nouns:

[singular] Ontem ouvi uma história interessante. Yesterday I heard an interesting story. [plural (no article)] Ontem ouvi histórias interessantes. Yesterday I heard interesting stories.

Instead, we use umas/uns to mean “some”:

Ontem ouvi umas histórias interessantes. Yesterday I heard some interesting stories.

Let’s now look at a few other contexts where we use the indefinite article. 

Comparison

We use the indefinite article when comparing someone to a well-known personality or entity:

Tu não és propriamente um santo! You are not exactly a saint!

Unfamiliarity

We also use the indefinite article to designate someone we don’t know very well (distance implied):

Hoje recebi uma chamada de um Jorge Amadeu. Today I got a call from someone called Jorge Amadeu.

Artworks

We use the indefinite article when referring to famous artists’ artworks (usually painters):

O Mário comprou um Picasso. Custou-lhe uma fortuna. Mário bought a Picasso. It cost him a fortune.

About & such

We use the indefinite article – specifically the plural forms umas/uns –  to mean “about” or “such”:

Hoje vi uns 15 golfinhos. Today I saw about 15 dolphins. Vens cá com umas idiotices! You come up with such nonsense!

Omission of the indefinite article

We usually leave out the infinitive article when referring to profession, rank, or nationality:

O meu primo é marinheiro. My cousin is a sailor. O João é tenente coronel. João is a lieutenant colonel. A Pernilla é dinamarquesa. Pernilla is Danish.

However, we use the infinitive article when we use modifiers:

O meu primo é um excelente marinheiro. My cousin is an excellent sailor. O João é um tenente coronel exigente. João is an uncompromising lieutenant colonel. A Pernilla é uma dinamarquesa típica. Pernilla is a typical Danish woman.

Contractions of the indefinite article

The indefinite articles will only contract with the prepositions em and de:

	uma	um	umas	uns
em	numa	num	numas	nuns
de	duma	dum	dumas	duns