Prepositions connect words and show the relationship between terms, such as place, direction, time, cause, purpose, and accompaniment. They always come before the complement and help indicate how an action is organized in the sentence. In Prepositions, this class appears as the base for more specific uses in Prepositions of Place, Prepositions of Time and Prepositions of Direction.

The most frequent prepositions are a, de, em, por, para and com. They introduce complements required by verbs, nouns and fixed expressions, and each tends to mark a type of relation. In many contexts, the exact meaning depends on verbal government and the sense of direction, place or purpose.

IdeiaIdea.	ExemploExample.
a indica direção ou destino.A indicates direction or destination.	Vou a Lisboa.I am going to Lisbon.
de indica origem ou posse.De indicates origin or possession.	Venho de casa.I come from home.
em indica localização ou permanência.Em indicates location or permanence.	Estou em casa.I am at home.
por indica passagem, causa ou agente.Por indicates passage, cause, or agent.	Passei por aqui.I passed by here.
para indica مقصد finalidade ou destinatário.Para indicates purpose or destination.	Estudo para o exame.I study for the exam.
com indica companhia ou instrumento.Com indicates accompaniment or instrument.	Vou com ele.I am going with him.

When a preposition combines with definite articles, the form usually changes to a contraction. The most common ones include a + o forming ao, de + o forming do, em + o forming no or na, and por + o forming pelo or pela. These forms are very frequent in speech and in everyday writing, and Prepositions of Place and Prepositions of Time use them very frequently.

IdeiaIdea.	ExemploExample.
a com o forma ao.A with the ao form.	Vou ao mercado.I'm going to the market.
de com o forma do.De with the do form.	Saí do trabalho.I left work.
em com os forma nos.In with the nos form.	Estamos nos jardins.We are in the gardens.
por com o forma pelo.por with the o form becomes pelo.	Seguimos pelo rio.We went along the river.
em com a forma na.Em with the na form.	Fico na escola.I am at school.
por com a forma pela.por with the form pela.	Caminhamos pela rua.We walked along the street.

Many verbs require a specific preposition, and this requirement is called verbal government. Verbs like gostar and precisar normally appear with de, while other verbs choose different prepositions according to the sense. The relation between verb and preposition is essential for natural constructions in Portuguese.

IdeiaIdea.	ExemploExample.
gostar pede de.To like requires de.	Gosto de música.I like music.
precisar pede de.To need requires de.	Preciso de ajuda.I need help.
telefonar pede para quando há destinatário.To call requires para when there is a recipient.	Telefonei para a Ana.I called Ana.
depender pede de.Depender requires de.	Depende do tempo.It depends on the time.
necessitar pede de.Need requires de.	Necessito de descanso.I need a rest.

Some relationships are expressed by fixed groups of words called prepositional phrases. Expressions such as por causa de, em vez de, and de acordo com function as a single preposition and introduce the complement after them. These locutions are very useful in Locuções Prepositivas and appear frequently in formal and neutral registers.

IdeiaIdea.	ExemploExample.
por causa de indica motivo.Por causa de indicates motive.	Cheguei tarde por causa do trânsito.I arrived late because of the traffic.
em vez de indica substituição.Instead of indicates substitution.	Fui a pé em vez de ir de carro.I went on foot instead of going by car.
de acordo com indica conformidade.De acordo com indicates conformity.	Tudo ficou de acordo com o plano.Everything went according to the plan.
perto de indica proximidade.Perto de indicates proximity.	Moro perto de casa.I live near my house.

After a preposition, tonic pronouns such as mim, ti, si, ele, ela, nós and vós are used. The fixed forms comigo, contigo, consigo and convosco appear only with certain prepositions and do not split into parts. In constructions with preposition, the correct form depends on the relation introduced by the preposition and not on the verb alone.

IdeiaIdea.	ExemploExample.
mim aparece depois de preposição.Mim appears after a preposition.	Trouxeram isto para mim.They brought this for me.
ti aparece depois de preposição.Ti appears after a preposition.	Falei contigo e com ti.I spoke to you and with you.
consigo aparece de forma fixa.Consigo appears as a fixed form.	Ele levou o livro consigo.He took the book with him.
conosco aparece como forma fixa.Conosco appears as a fixed form.	Venha conosco ao cinema.Come with us to the cinema.
com ele mantém a forma normal.With him, it keeps the normal form.	Saí com ele.I left with him.

The preposition appears before its complement and never after it. When para comes before an infinitive, the phrase normally expresses purpose, such as to study, to help, or to solve something. In movement and direction structures, the choice between por and para depends on the sense one wants to mark, and usage varies quite a bit between informal speech, neutral writing and more formal registers.

IdeiaIdea.	ExemploExample.
para antes de infinitivo expressa finalidade.Para before an infinitive expresses purpose.	Estudo para aprender.I study to learn.
para antes de infinitivo indica propósito.Para before an infinitive indicates purpose.	Fui cedo para comprar pão.I went early to buy bread.
a preposição vem antes do complemento.The preposition comes before the complement.	Vou a casa.I am going home.
por pode indicar causa ou passagem.Por can indicate cause or passage.	Fiz isso por amor.I did this for love.
para pode marcar prazo ou destino.Para can mark a deadline or destination.	O trabalho é para amanhã.The work is for tomorrow.

In colloquial speech, de can contract with um and uma, forming dum and duma. These forms are common in speech and informal registers, but are avoided in formal writing. The same alternation between formality and everyday use also appears in the choice between por and para in different regions and contexts.

RegiãoRegion.	FormaForm.	Definição regionalRegional definition.	ExemploExample.
OralOral.	dumOf a.	Forma coloquial de de um usada na fala informal.Colloquial form of de um used in informal speech.	Ele saiu dum jeito apressado.He left in a hurry.
OralOral.	dumaOf a.	Forma coloquial de de uma usada na fala informal.Colloquial form of de uma used in informal speech.	Veio duma casa antiga.Came from an old house.
FormalFormal.	de umOf a.	Forma preferida na escrita formal.Preferred form in formal writing.	Preciso de um copo.I need a glass.
FormalFormal.	de umaOf a.	Forma preferida na escrita formal.Preferred form in formal writing.	Gosto de uma solução clara.I like a clear solution.

Prepositions organize essential relationships among the elements of the sentence and always appear before the complement. The basic forms, the contractions with articles, verbal government, prepositional phrases and tonic pronouns show how Portuguese links meaning and structure. To interpret place, time and direction well, it is also useful to recognize the specific value of por, para and the most frequent contractions.