CONDITIONAL SENTENCES (TYPE 1 &2)

MEANING

FIRST CONDITIONAL

Condition possible to fulfill (likely condition)

SECOND CONDITIONAL

Condition in theory possible to fulfill (Unlikely condition)

FORM

type	if clause	main clause
I	Simple Present	will-future (or Modal or imperative)
II	Simple Past	would /could+ infinitive

EXAMPLES

If I find her address, I will send her an invitation(Type 1: It is possible and likely that the condition will be fulfilled)

If I found her address, I would send her an invitation (Type 2: It is possible but unlikely that the condition will be fulfilled)

First conditional (present simple /will+infinitive or imperative)

If you see Sue, tell her I need to talk to her.

If he gets up early, he will go by bus.

Second conditional (past simple/would, could +infinitive)

If I had his number, I could call him. 

If I were you, I wouldn't go out with that man.