Conditionals  ( Typical Constructions )

Type Zero ( 0 )

        If ( present simple ) / ( present simple )

    For logical conclusions , scientific facts, general truth.

        If you press the pause button, the cd doesn't play.

        If you heat water at 100ºc, it boils.

Type 1

           If ( present simple ) / will + verb ( can / may )

        If ( present simple ) / imperative

    For real possibilities. It's a real condition.

        If I get a raise, I'll buy a new car

        Take the message, if someone calls.

Type 2

        If ( past simple ) / would + verb ( could / might )

    For unreal present. It's an unreal condition.

        If I got a raise, I'd buy a new cae ( = I'm not getting a   raise, so I can't buy a new car )

        If I didn't study hard, I wouldn't get good marks ( = I study hard and get good marks ).

Type 3

        If ( past perfect ) / would + have + verb ( past participle )

                                   ( could / might )

    For unreal past. It's an unreal possibility.

        If  I hadn't gotten a raise, I wouldn't have bought a new car ( = I got a raise so I bought a new car )

        If he had studied harder, he'd have passed ( = He didn't study hard so he didn't pass )

Mixed ( Types 2/3  or  3/2 )

        If you were my friend, you would have invited me. ( = You aren't my friend (T.2) so you didn't invite me (T.3)

        If my friends hadn't supported me,  I would be unemployed today ( = My friends supported me (T.3) so I'm employed today (T.2) ).