ملخص الدرس / الثآنية ثانوي/اللغة الإنجليزية/Grammar/If-conditional

If is a conjunction which introduces a condition (something which may or may not happend depending circumstances).

there are four mainkinds of condition.

if-conditional :type zero

form: if+.....present simple.....,.....present simple....

Meaning:

this type of condition has the present simple in both clauses,and means that the conditional can be true at any time .in this type of condition,if can be replaced by when or whenever.

if , when, whenever you heat water at 100 degrees celsius, it boils .

water boils if , when, whenever you heat at 100 degrees celsius.

note:

when if means if it is true that, the present simple does not describe some thing true at any time or a  general habit. so when can not replace if.

if= if it's true that when you take this medecine, you will soon fell better . 

form:

if+....present simple ...,....,will (or'll)will not (or won't).

if I SEE Abedelkaderm Iwill invite him to the party.

We'll go to the beach tomorrow if it sunny.

Meaning:

We use the first conditional to talk about thingsthat are possible in the future.it's possible that it will be sunny .so likely result  we'll go to the beach tomorrow.

note:we do not use willin the if clause, even though it refers to the future.

if I will pass my brevet, I'will celebrate. 

form:

if....+past simple...,+would (or 'd).

if Iwere you ,Iwould apologise.

if the Martians invadedour planet one day,they'd kill us all.

Meaning:

we use the second conditional to talk about the present, and to imagine something totally different from the real situation now or in the future.

in sentence a,the speaker is just imagining  himself/herself that he is me.but he can't really be me.

in sentence b, the speaker is just imagining that one day the Martians will invade our plante. but we know well that Martians do not exist.

Note: you can use were for alls forms of be  in the if clause of the second conditional.

if she/he /karim was /were rich,he/she would travelto Australia.  

form:

if +......past perfect...,.....'d/would  have .....+past participle......

Meaning:

if I had been a littel bit taller,I'd/would have joined the Army.

I'd/would have joined the Army if I had been a littel bit taller.

We use type 3 conditional when we imagine a different past,i.e,an nureal past. in the example above, the speaker was not tall enough.so he could not join the Army.

if+present simple,     imperative       .

if you're happy,  clap your hands.

if +present +modal+verb

if you fall, you can/may hurt yourself.

if it fails to start ,you should/must check the battery.

if +past simple+might/could+ verb 

if Martians invaded our plane, they could exterminate us.

if+past perfect +might/could+have +past participle.

if she know about your difficulties, she might have helped you.