Proper Use of the Apostrophe to Show Omission of Letters (Contractions)In contractions , the apostrophe is used to show the omission of one or more letters.
Again, be careful not to confuse contractions with possessive pronouns.
Contractions also may be used to omit letters or numbers at the beginning of words or dates:
Electing to use a contraction versus the full form of the words depends on the audience and the context of the writing. In most formal settings (including business settings), it is better to use the full form of the words, while in a familiar setting, the contractions may be used.