Basic contractions: do, da, no, na, pelo, pela

DE Contractions (of/from + the)

These express possession, origin, and characteristics.

Formation:

• de + o = do (of/from the - masculine singular)
• de + a = da (of/from the - feminine singular)
• de + os = dos (of/from the - masculine plural)
• de + as = das (of/from the - feminine plural)

Common uses:

• Possession: O carro do Paulo (Paulo's car)
• Origin: Ela é do Brasil (She's from Brazil)
• Part of something: A porta da casa (The door of the house)

EM Contractions (in/on/at + the)

These indicate location and time.

Formation:

• em + o = no (in/on/at the - masculine singular)
• em + a = na (in/on/at the - feminine singular)
• em + os = nos (in/on/at the - masculine plural)
• em + as = nas (in/on/at the - feminine plural)

Common uses:

• Location: Estou no hotel (I'm at the hotel)
• Surface: O livro está na mesa (The book is on the table)
• Time: No domingo (On Sunday)

POR Contractions (by/through/along + the)

These show movement through, agent, or route.

Formation:

• por + o = pelo (by/through the - masculine singular)
• por + a = pela (by/through the - feminine singular)
• por + os = pelos (by/through the - masculine plural)
• por + as = pelas (by/through the - feminine plural)

Common uses:

• Route: Ando pela rua (I walk along the street)
• Agent: Feito pelo professor (Made by the teacher)
• Through: Entrou pela porta (Entered through the door)

Gender and Number Agreement

The contraction must match the noun's gender and number:

• Masculine singular: do livro, no carro, pelo caminho
• Feminine singular: da mesa, na escola, pela janela
• Masculine plural: dos meninos, nos parques, pelos correios
• Feminine plural: das meninas, nas lojas, pelas ruas

When NOT to Contract

No contractions with:

• Indefinite articles: de um, em uma (NOT dum, numa in formal writing)
• Demonstratives: de este, em esse
• Possessives when the article is optional: de meu, em seu