In contractions, an apostrophe normally replaces omitted letters. Examples: don’t, can’t, won’t, shouldn’t, wouldn’t. Other examples are: singin’, ’tis, and rock ‘n’ roll. Some contractions, such as won’t or ain’t, are formed irregularly. Colloquialisms such as gonna and wanna take no apostrophe since there is no place for one.
To avoid confusion, lowercase letters form the plural with an apostrophe and an “s.” Example: x’s and y’s.
In informal writing the first two digits of a particular year are often replaced by an apostrophe. Example: the class of ’62.
Whenever you are using an apostrophe, be sure to use the symbol for an apostrophe and not use the symbol for a single quotation mark. They are different: ( “ ‘ ” vs. “ ’ ”).
This concludes the four-part series on apostrophes.