Use contractions to shorten common phrases or combinations of words. Most common contractions include a verb. Apostrophes are always placed in the space where letters have been removed in the contraction. For example, in the contraction of "can not," the letters "n" and "o" are removed from "not" and an apostrophe is put in their place to form the word "can't." You can use an apostrophe to contract numbers, such as years, also, in situations in which the century to which you are referring is clear. For example, the year 1950 can also be written as '50 in informal contexts in which it is understood that you are referring to the 20th century.
Many verb contractions are formed with a common verb and the word "not." For example, "have not" becomes "haven't." Some verb contractions have irregular forms, for example, the contraction of "will not" is "won't." Another common type of contraction contains a pronoun and the word "will." For example, "you will" is contracted into the word "you'll." Pronouns and a conjugated form of the verb "to be" are often used in contractions, such as "we are" becoming "we're." In all verb contractions, the second word is shortened and attached to the first with an apostrophe in place of the missing letter or letters.
Some contractions are notable for being a little different from the more straightforward contractions. Contractions with pronouns and the verb "to have" include irregular endings, such as "I've" and "he's." People often confuse the contraction "it's," meaning "it is," with the possessive pronoun "its," because many nouns can be made possessive by adding an apostrophe followed by an "s." Contractions also exist in words other than common verb phrases, such as "o'clock" to designate hours (the shorter version of "of the clock") and "ma'am" (short for "madam").
A traditional rule of formal writing is to avoid using contractions and to write out the full phrase instead. This rule has become debatable over time, but to be safe, it is better to avoid using contractions in academic and professional writing. Use contractions for informal writing, such as email and informal letters, but if you are writing an essay for school, a business proposal or a resume, do not include contractions. In creative writing, such as poems and stories, the use of contractions is acceptable if you choose to include them, as creative writing is an art form and usage is based on the author's preference. Dialogue between characters also seems more natural when contractions are included in their speech.