In short

The little words for “the” and “a” (o, a, os, as and um, uma, uns, umas) must agree in gender and number with their noun, so they lean directly on noun gender and number. The twist that has no English equivalent: when the prepositions de, em, a and por meet an article, they fuse into a single word - de + o -> do, em + a -> na, a + a -> à. These contractions are not optional shortcuts; the separate spelling “de o” simply does not exist, so learn the fused forms as the real words.

The rule

The two articles

The definite article (English “the”) has four forms; the indefinite (English “a / an”, plural “some”) has four too. Pick the one that matches the noun’s gender and number:

• o livro, a casa, os livros, as casas - “the”.
• um livro, uma casa, uns livros, umas casas - “a book, a house, some books, some houses”.

European Portuguese uses the definite article in several places where English drops it. It appears before whole classes and abstract nouns (O café faz mal - “Coffee is bad for you”; Adoro a música - “I love music”), before most country names (a França, o Brasil, os Estados Unidos - but bare Portugal, Angola, Moçambique), and, very typically, before people’s first names in everyday speech (A Joana chegou - “Joana has arrived”). It is also kept before possessives (o meu carro - “my car”), a point you meet fully in Lesson 4.

The indefinite article is dropped before an unmodified profession or nationality after ser: Sou professor, Ela é portuguesa. Add it back only when there is a describing word: Ela é uma médica excelente.

Contractions with the definite article

This is the heart of the lesson. Four prepositions must contract with o, a, os, as:

• de (of / from) -> do, da, dos, das
• em (in / on / at) -> no, na, nos, nas
• a (to / at) -> ao, à, aos, às
• por (by / through / for) -> pelo, pela, pelos, pelas

So “the man’s book” is o livro do homem, “in the city” is na cidade, “to the cinema” is ao cinema, and “along the street” is pela rua. Writing de o, em a, a o or por a is always wrong.

The à contraction (a + a)

When the preposition a meets the feminine article a, the two merge and the fusion is written with a grave accent: a + a -> à, a + as -> às. The accent is the visible sign that two a’s have become one; it is obligatory, not decorative:

• Vou à praia - “I am going to the beach” (a + a praia).
• Chegámos às oito - “We arrived at eight” (a + as horas).

Contrast Vou a Lisboa - cities usually take no article, so there is no second a to swallow and no accent. The masculine equivalent is simply ao (Vou ao Porto).

Contractions with the indefinite article

em also contracts, obligatorily, with um / uma:

• em -> num, numa, nuns, numas: Moro numa aldeia - “I live in a village”.

de may contract with um / uma (dum, duma), and both de um and dum are accepted in Portugal. The prepositions a and por do not contract with the indefinite article: a um amigo, por uma razão.

Contractions with demonstratives

The same three prepositions de, em and a fuse with the demonstratives (este, esse, aquele; the neuters isto, isso, aquilo), which you study in full in Lesson 4:

• de: deste, desse, daquele; disto, disso, daquilo.
• em: neste, nesse, naquele; nisto, nisso, naquilo.
• a: only the aquele-series contracts, taking the grave accent: àquele, àquela, àquilo. After a, the near forms stay open: a este, a esse.

Forms & patterns

Definite and indefinite articles:

Preposition + definite article (all obligatory):

Preposition + indefinite article and demonstratives:

Examples

Common mistakes

• de o professor -> do professor - de, em, a and por always fuse with the article; “de o”, “em a”, “a o” never appear.
• Vou a a praia -> Vou à praia - the two a’s merge into à, and the grave accent is obligatory.
• em uma casa -> numa casa - em always contracts with um / uma (num, numa); the split form sounds heavy in EP.
• a aquele homem -> àquele homem - only the aquele-series contracts after a, and it carries the grave accent (àquele, àquela, àquilo).
• o livro de o meu pai -> o livro do meu pai - the article stays and still contracts even before a possessive: de + o -> do.
• Falei co o Pedro -> Falei com o Pedro - com, para and sem do NOT contract with the article; do not overapply the rule.
• Vou à Lisboa -> Vou a Lisboa - cities take no article, so there is no second a and no accent; à appears only when a real feminine article is present.

Tips

• Drill the four obligatory rows as one block: de -> do/da/dos/das, em -> no/na/nos/nas, a -> ao/à/aos/às, por -> pelo/pela/pelos/pelas. Treat “de o” as a spelling that does not exist.
• Hear à as a slightly longer, more open “a” than plain a; that stretched vowel (recall the reduced vowels from the reading & pronunciation guide) is your ear’s cue that a preposition has swallowed an article.
• After de, em or a, always contract a following demonstrative: deste, nesse, àquele. Remember that a fuses only with the aquele-series.
• Only de, em, a and por contract; com, para, sem, sobre and entre stay separate before the article.
• The name “crase” for the a + a -> à fusion is the usual school label in Brazil; Portugal knows the term too, but there you more often hear “a com acento grave” - the rule is identical, only the everyday label differs.
• In Brazil: num / numa are used the same way, but de um is preferred over dum, and dropping the article before first names (Falei com Joana, not com a Joana) is common.