The term contraction refers to a short form in which a subject and an auxiliary verb or a verb and the word ‘not’ are joined together into one word. Examples are:
I’m (= I am)
can’t (= cannot)
won’t (= will not)
we’d (= we would/had)
I’m tired. = I am tired.
I’ve no idea. = I have no idea.
My father’s not well. = My father is not well.
Contractions are common and correct in informal speech. They are not normally used in formal writing.
In non-standard English, ain’t is used as a contraction of am not, are not, is not, have not and has not.
• I ain’t going to tell him. (=I am not going to tell him.)
•Don’t talk to me like that – you ain’t my boss. (=You aren’t my boss.)
A clause or sentence containing if (or a word with a similar meaning) and often a conditional verb form.
If I get a promotion, I will buy a car.
If you try, you will understand.
What would you have done if the train had been late?