Modal auxiliaries: indicate potential or uncertain.
Will/would(used to), can/could, may/might, shall/should, must(have to/had to)
In parenthesis() are semi modals/same as meanings but not grammatically same.
The real-factual and habitual and the unreal-contrary to fact or hypothetical.
If I have the time, I will go. (I will go unless I don’t have time)
I will play tennis unless I have a headache. (if my headache disappears, we can play tennis)
If I had time, I would go.
(I cannot go, this is contrary to fact)
We could go out tonight if we dint have to study.
(both sentences mean: we cant go out tonight because we have to study.)
Can never be “was”. Always “were” in correct English(In conditional.)
In unreal conditional sentences, if sentence is negative, meaning=positive. If sentence positive, meaning= negative. If I were reach, I would travel around the world.( I am not reach so I am not going to travel around the world)
If I hadn’t been in a hurry, I wouldn’t have spilled the milk.( I was in a hurry. I spilled the milk)
Past perfect is followed by modal + perfect+pp.
Real conditions (possibly true)
Future: if I have the money, I will buy a new car.
Habitual: john usually walks to school if he has enough time.(no modal)
Command; if you go to the post office, please mail this letter for me.(simple form of verb)
Unreal conditions (untrue)
If I had……., I would……….
If I were……..,I would……
If he dint…….., you could……..
Past: if we had known that you were there, we would have written you a letter.
Or, Had We known that you were there, we would have written you a letter.