It's is short for "it is'
I've ~ I have
Wasn't ~ Was not
Contractions are similar with abbreviations.
Abbreviation is a shortened form of a word or phrase. The letters forming the abbreviation are taken from the long version of the word. Here are some common abbreviations used:
Mr. - Mister
Mrs. - Mistress; feminine equivalent of Mister.
Ms. - Miss
Prof. - Professor
Rev. - Reverend
PM or p.m. - post meridiem
AM or a.m. - ante meridiem
A.D. - anno Domini
B.C. - before Christ
USD - United States Dollar
CAD - Canadian Dollar
B.A. - Bachelor of Arts
B.S. - Bachelor of Science
