Das Verb ir und das nahe Futur

Ir is "to go", and it is irregular from top to bottom: no form looks like the infinitive. It is worth the effort, because with an infinitive after it, ir is also the everyday way to talk about the future.

Vou ao mercado. Vamos à praia? Eles vão de ônibus. - by bus is de ônibus (in Portugal, de autocarro), on foot is a pé. Vamos! on its own is "Let's go!"

The future with ir

Present of ir + infinitive, exactly like English "going to":

• Eu vou estudar amanhã. - I'm going to study tomorrow.
• Ela vai viajar para Portugal em julho. - She's going to travel to Portugal in July.
• A gente vai comer fora hoje. - We're eating out tonight.

In spoken Brazilian Portuguese this is the normal future for almost everything. The single-word future (estudarei, viajará) belongs to news, contracts and speeches. "I'm going to go" is fine too: Vou ir is heard in Brazil, but the standard way is just Vou.

The verb after vou stays in the infinitive. *Vou estudando is not the future; ir + gerund means "gradually doing": A gente vai aprendendo - "we learn bit by bit".

Going to: a or para?

Textbooks say ir a is for a short trip and return, ir para for going to stay: Vou ao banco (and back), Ele vai para o Brasil (to live). That is a fair description of careful usage, especially in Portugal. In everyday Brazilian speech para, usually shortened to pra, is used for both: Vou pro banco, Vou pra casa. What you cannot do is use em for direction in writing: Vou no mercado is very common colloquially in Brazil but marked as non-standard.

Where English speakers slip

• Forgetting the contraction: a + o = ao, a + a = à: Vou ao cinema, Vou à farmácia.
• Using Estou indo for every plan. Estou indo means you are on your way right now; for plans, use Vou.