Many visitors and subscribers ask us: I was told there are three or four conditionals in English, but I suppose I know just one. It is true, there exist THREE different types of conditional sentences in English. Let's study them here...

Muchos visitantes y suscriptores nos consultan: Me dijeron que hay tres o cuatro tipos de condicionales pero creo saber sólo uno. Es cierto, básicamente existen CUATRO tipos de condicionales en inglés que analizamos aquí...

conditional type I >> FIRST CONDITIONAL                             

Used to talk about things which are possible in the present or the future. It is generally used for things which may happen (utilizado para cosas que pueden ocurrir en presente o futuro).

a)  IF  + SIMPLE PRESENT  +  SIMPLE FUTURE 

If you study hard, you will pass your exams. 
Si estudias intensamente aprobarás tus exámenes. 

If we do not protect the panda bears, they will soon become extinct. 
Si no protegemos a los osos panda, pronto se extinguirán.

b)  IMPERATIVE  +  OR / AND  +  SIMPLE FUTURE
Used for threats and promises (usado para expresar amenazas y promesas)

Don't say a word about this, or I will kill you. 
No cuentes una palabra de esto o te mato.

Finish your job, and you will have a bonus. 
Termina tu tarea y tendrás una gratificación.

c)  IMPERATIVO  +  IF / IN CASE  +  SIMPLE PRESENT

Contact me if you need any help. 
Ponte en contacto conmigo si necesitas ayuda.

Call them in case you need help. 
Llámalos en caso de necesitar ayuda.

NOTE: In cases b and d above, you can replace IF (si) by UNLESS (a menos que)

conditional type II >> SECOND CONDITIONAL         

Used to talk about things which are unreal (not true or not possible) in the present or the future. It is generally used for things which don't or won't happen. It is generally used for things which may happen (utilizado en presente o futuro para expresar situaciones hipotéticas, que normalmente son irreales o imposibles).

IF  +  SIMPLE PAST  +  SIMPLE CONDITIONAL 
If FIRST verb in the sentence is TO BE, WERE is used for all persons. 
(Si el PRIMER verbo de la oración es TO BE, se usa WERE para todas las personas)

If I were rich, I would buy a castle. 
Si fuera rico, compraría un castillo.

If I were him, I would go and see a doctor. 
Si fuera él -en su lugar- consultaría con un médico.

If elephants had wings, they would be able to fly. 
Si los elefantes tuvieran alas, podrían volar.

NOTE: You can replace IF (si) by UNLESS (a menos que) in the examples above.

conditional type III >> THIRD CONDITIONAL

Used to talk about unreal situations in the past, that is, things which did not happen in the past. (utilizado para expresar situaciones irreales – que nunca sucedieron – en el pasado y, en general, dentro de un contexto de crítica, queja o remordimiento). En español tienes una construcción similar por lo cual este condicional no debería resultar complicado.

IF  +  PAST PERFECT  +  CONDITIONAL PERFECT 
If FIRST verb in the sentence is TO BE, WERE is used for all persons. 
(Si el PRIMER verbo de la oración es TO BE, se usa WERE para todas las personas)

If I had known that you were sick, I would have gone to see you. 
Si hubiese sabido que estabas enfermo, te habría ido a ver.

The real situation was that I didn't know you were sick. So I say If I had known... When you are talking about the past, you use the Past Perfect (I had known) after IF.

If you had saved your money, you could have bought a laptop. 
Si hubieses ahorrado tu dinero, podrías haberte comprado una computadora.

The real situation was that you didn't save your money. So they say If you had saved... When you are talking about the past, you use the Past Perfect (I had known) after IF.

If you hadn't been late for work so often, they wouldn't have fired you. 
Si no hubieses llegado tarde al trabajo tan seguido, no te habrían despedido.

The real situation was that you wasn't early for work. So they say If you hadn't been late... When you are talking about the past, you use the Past Perfect (I had known) after IF.

NOTE: You can replace IF (si) by UNLESS (a menos que) in the examples above.