1. There are 4 types of CONDITIONAL SENTENCES:
ZERO TYPE (true evidences and rules)
•If you heat water over 180º, it boils
•If you eat too much fat, you usually put on weight
CONDITION CONSEQUENCE
(SEE: You usually put on weight if you eat too much fat)
IF + PRES. + PRES. or
PRES. + IF + PRES.

2. FIRST TYPE (real situations which may happen)
* If the expedition reaches the Everest today, they will
return in a week
* Susan will bake a cake for the birthday party
if she doesn´t forget
IF + PRES. + FUT. (WILL) or
FUT. (WILL) + IF + PRES.

3. SECOND TYPE (unreal or imaginary situations)
* If you didn´t study so much, you wouldn´t pass all
subjects (so you study hard and you pass)
* I would carry a bigger suitcase if I needed it
(so I don´t need a bigger suitcase)
IF + PAST SIMPLE + WOULD+ V (INF) or
WOULD + V (INF) + IF + PAST SIMPLE

4. THIRD TYPE (situations which didn´t happen in the
past)
* If you hadn´t been born in Munich, you wouldn´t
have spoken German (you were born in Munich, so
you speak German)
* Mary would have chosen a different dress for the
wedding if she had known it was the same as
yours (she didn´t know, so she wore the same
dress)
IF + PAST PERF. + WOULD HAVE + PARTIC. or
WOULD HAVE + PARTIC. + IF + PAST PERF.