CONDITIONALS 

ZERO CONDITIONAL

If you freeze water, it turns into ice.

If clause	Main clause
If + Present tense	Present tense
If you freeze water	it turns into ice.

• If you freeze water, it turns into ice.
  Si congelas el agua, se convierte en hielo.
• If I work too much, I get tired. 
  Si trabajo demasiado, me canso.
• If I have time, I usually go to the movies.
  Si tengo tiempo, generalmente voy al cine.
• If she eats hamburgers, she gets an allergy.
  Si ella come hamburguesas, le da alergia.
• If they come here, they always bring a present.
  Si ellos vienen aquí, siempre traen un regalo.
• If she doesn't know the answer, she keeps silent.
  Si ella no sabe la respuesta, se mantiene en silencio.
• If we don't go out on Saturdays, we rent a video and stay home.
  Si no salimos los sábados, alquilamos un video y nos quedamos en casa.

FIRST CONDITIONAL

If it rains today, I'll stay at home. Aquí tienes algunos ejemplos traducidos.

If clause	Main clause
If + Present tense	will / can / may / must + verb
If it rains today,	I'll stay at home

• 
  
• If it rains today, I'll stay at home.
  Si llueve hoy, me quedaré en casa.
• If he is busy now, I will come back tomorrow.
  Si está ocupado ahora, regresaré mañana.
• If I have time, I'll visit my parents this afternoon.
  Si tengo tiempo, visitaré a mis padres esta tarde.
• If it is warm tomorrow, we'll go to the beach.
  Si está caluroso mañana, iremos a la playa.
• If it is cold, you must wear warm clothes.
  Si está frío, debes usar ropa abrigada.
• If he doesn't do his homework, he can not go to the party.
  Si él no hace su tarea, no puede ir a la fiesta.
• If she doesn't call you, you can call her.
  Si ella no te llama, tú puedes llamarla.
• If you work hard, you may become a millonaire someday.
  Si trabajas duro, puede que te conviertas en un millonario algún día.

SECOND CONDITIONAL 

if + simple past + simple condicional

• If I were in Brazil, I would go to Rio de Janeiro.
  Si yo estuviese en Brasil, iría a Río de Janeiro.
• If I were you, I would buy that car.
  Si yo fuese tú, compraría ese auto.
• If he were in my place, he wouldn't do this.
  Si él estuviese en mi lugar, no haría esto.
• If I had more money, I would buy a nice apartment.
  Si yo tuviese más dinero, me compraría un lindo apartamento.
• If she had more time, she would travel more often.
  Si ella tuviera más tiempo, viajaría más a menudo.
• If it were not raining, we could go out.
  Si no estuviese lloviendo, podríamos salir.
• If we didn't have to work today, we could have a picnic.
  Si no tuviésemos que trabajar hoy, podríamos tener un picnic.

THIRD CONDITIONAL

If clause	Main clause
If + Past Perfect tense	would/could/might + have + past participle
If I had won the lottery,	I would have traveled around the world.

• If I had won the lottery, I would have traveled around the world.
  Si yo hubiera ganado la lotería, habría viajado por todo el mundo.
• If I had seen him, I would have told him about you.
  Si lo hubiese visto, le habría contado acerca de ti.
• If I had known the answer, I would have raised my hand.
  Si hubiese sabido la respuesta, habría levantado mi mano.
• If she had come on Saturday, I would have seen her.
  Si ella hubiese venido el sábado, la habría visto.
• If they had left earlier, they would have arrived on time.
  Si ellos hubiesen salido más temprano, habrían llegado a tiempo.
• If we had studied harder, we might have passed the test.
  Si hubiésemos estudiado más duro, podríamos haber aprobado la prueba.
• If you had gone to Brazil, you would have had lots of fun.
  Si tu hubieses ido a Brasil, habrías tenido mucha diversión.
• If I hadn't been so busy, I could have helped you.
  Si no hubiese estado tan ocupado, te podría haber ayudado.

RELATIVE PRONOUNS

A relative pronoun is a pronoun used to mark a relative clause, and having the same referent as the element of the main clause (usually a noun or noun phrase) which the relative clause modifies.

An example is the English word which in the sentence "This is the house which Jack built." Here which Jack built is a relative clause modifying the noun house. The relative pronoun which marks the relative clause and refers (within the relative clause) to the man being referred to in the main clause. It can be considered to provide a link between the two sentences "This is a house" and "Jack built the house", where the house referred to in each case is the same.

(5) This is a bank. This bank accepted my identification.

(6) She is a bank teller. She helped us open an account.

With the relative pronouns, sentences (5) and (6) would read like this:

(7) This is the bank that accepted my identification.

(8) She is the bank teller who helped us open an account.