A classificação mais comum das if clauses (conditional clauses) é a seguinte:

0) Zero conditional

- Uso: Certas condições sempre manifestam os mesmos efeitos, ou seja, são verdades gerais. É bastante usado para falar de verdades científicas ou fenômenos da natureza.

- Estrutura: if + present + present

- Exemplo: If you heat water to 100 degrees, it boils.

1) First conditional (present real conditional)

- Uso: Uma condição presente manifestará seus efeitos no futuro. Desse modo, ainda é completamente possível que essa condição se materialize.

- Estrutura: if + simple present + will
- Exemplo: If it rains, I will stay at home.

2) Second conditional (present unreal conditional)
- Uso: Uma condição passada manifesta seus efeitos no presente. Como a condição é passada, provavelmente não mudará mais. Entretanto, em alguns casos, ainda há uma pequena esperança de que essa condição se materialize "de última hora" e manifeste seus efeitos ainda no presente (o que é bastante improvável, mas não impossível). Pode-se pensar também que é teoricamente possível que a condição se materialize.

- Estrutura: if + simple past + would
- Exemplo: If I had money, I would travel.

3) Third conditional (past unreal conditional)
- Uso: Uma condição em um passado remoto manifestou seus efeitos em um passado mais recente. Nesse caso, tanto a causa quanto a consequência já ocorreram e não podem mais ser alteradas. Só resta a possibilidade de imaginar o que teria acontecido no passado caso a condição do passado remoto tivesse sido diferente.

- Estrutura: if + past perfect + would have
- Exemplo: If I had studied, I would have passed the exam.

Nota: Como já discutido nesse fórum, essa divisão rigorosa entre os tipos de condicional é artificial. É apenas uma tentativa de classificar os casos mais comuns em que nativos usam frases condicionais. Um falante nativo do idioma pode facilmente criar frases condicionais que não sigam a nenhum dos padrões acima e que transmitam idéias bem mais complexas. Para um estudante de inglês, entretanto, estudar os padrões acima é uma boa forma de começar.

M Rob,

I understand what you say and I agree with most of it. I realize that grammar is always an artificial attempt to classify language, which is a natural phenomenon. Therefore, grammar is oftentimes imprecise and incomplete if compared to the vast possibilities that can be created by a native speaker of the language. I also agree that the three classical types of conditional statements are an artificial limitation that has a sole purpose: making learning and teaching language easier.

However, I don't really understand how a sentence like “If I were in Brazil, I wouldn't have done that” can be considered correct. In this case, grammar is not the only limiting factor; the sentence also contradicts logic. I have a really hard time understanding how a present cause can have a consequence in the past. Am I the only one who finds that illogical? Are you saying that a native speaker may use that sentence when he wants to imply a present unreal condition or that this logic paradox may be acceptable in certain contexts? Actually, I can’t think of any situation where I’d use a sentence in which a present condition leads to a past consequence. Am I missing something? I’d really appreciate further clarification on this matter.

Thanks,

Tiago

If you look up 'if clauses'  here on EMB you will find the following, which answers your question, I think

Algumas orações condicionais (if clauses) também são resquício do English subjunctive. A classificação mais comum das if clauses é assim:

1) First conditional (present real conditional)
if + simple present + will
If it rains, I will stay at home.

2) Second conditional (present unreal conditional)
if + simple past + would
If I had money, I would travel.

3) Third conditional (past unreal conditional)
if + past perfect + would have
If I had studied, I would have passed the exam.

Before discussing the subjunctive, the pattern of English verb use is:

· Present reality – base verb form (go, see etc)

· Present unreality – remote verb form (went, saw etc)

· Past reality – remote verb form (went, saw etc)

· Past unreality – remote verb form with perfect aspect (had gone, had seen etc)

These forms can also be combined with either or both of the two aspects (continuous and perfect) and the various auxiliaries (will, would can, could etc) and other pieces (had to, used to, going to, etc) for a range of meanings 

Any ambiguity arising from the recycling of verb forms (the Present unreality and Past reality forms are identical) is resolved through adverbs and context.

In spoken English the above pattern is usually sufficient to convey meaning adequately.

So what we can say if we compare English with French, Italian, and Portuguese etc is that we can see that the English verb is a minimalist verb (no separate distinct future forms, but a range of forms for referring to the future) and that there are many other structural deficits (when compared with the range of verbs forms in those other languages)

Likewise there is no distinct subjunctive form, just a recycling of the base verb forms (go, went, had gone) without an inflection for third person singular in the present reality context. (and use of were instead of was)

The so-called English subjunctive is treated like a holy relic, a ‘sacred cow’ because it allows speakers of the hybrid ‘bastard’ tongue English to pretend that our language derived from the esteemed classical languages Greek and Roman.

The value of the subjunctive to English is that it confers a cultural credibility and prestige which would otherwise be lacking for the ‘English’ barbarians who were lucky enough to establish a ‘pretty big’ naval empire in the wake of the Portuguese, Dutch, Spanish etc) – and hence spread their lingo

So, as with the emperor’s new clothes, we can all see that the so-called English subjunctive is merely a recycling of the limited range of verb forms in situations referring to unreality, or intent

But don’t let the cat out of the bag………….

1) I suggest that she wear a pair of sturdy blue jeans.
2) I suggest that she visits her GP and gets a prescription .
3) I suggest that she be preserved.
4) I suggest that she is mistaken.
  
Qual das formas é a correta? Quando tenho 3a. pessoa do singular eu devo sempre conjugar o verbo? Alguma delas é formal e a outra informal?

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As frases (1) e (3) estão certas e a estrutura usada (English subjunctive) é característica da linguagem formal, principalmente escrita. As frases (2) e (4) estão erradas segundo a gramática formal, já que nelas o verbo foi conjugado (e não mantido no infinitivo). Entretanto, essa estrutura é bastante encontrada em conversação informal. Na verdade, eu não entendi muito bem o significado da frase (4), mas considerei só a gramática.

Algumas estruturas de frase exigem o uso do present subjunctive, que consiste em usar o verbo no infinitivo (sem conjugação). Leia o meu tópico abaixo para mais exemplos:

http://www.sk.com.br/forum/display_message.php?message_id=24199

Mariana escreveu:
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1) Present Subjunctive - I insist that he go now.
2) Past Subjunctive - If I had the time, I would work out more often.
3) Past Perfect Subjunctive - If I had known it was going to rain, I would have brought an umbrella.
 

E a frase: "If I have time, I will work out more often".  Isto é "Future Subjunctive"? Que tempo verbal é esse em inglês?

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