In English, a contraction is an abbreviated word formed by removing a letter or multiple letters from a longer word or phrase. The omitted letters are replaced by an apostrophe. For example, he’s is a contraction of he is, won’t is a contraction of will not, o’clock is a contraction of of the clock, and y’all is a contraction of you all.
Are contractions informal?
There is a longstanding superstition that contractions are always out of place in formal or serious writing. This may be a good rule for very formal contexts, especially when you are not familiar with your audience and need them to take you seriously, but outside very formal writing, there’s no good reason to avoid contractions. Yes, they create a breezier, more speech-like tone, but there’s nothing improper about that. In fact, using the noncontracted versions can sound overformal.
For example, these major news publications have no prohibitions against contractions in most of their stories:
His Nepali guide insists he won’t marry a village girl but vigorously defends the interests of his 13-year-old sister. [New York Times]
Outsourcing isn’t always the best option. [Guardian]
The Labor Party didn’t fare well in the local government elections held across NSW last weekend. [Sydney Morning Herald]
And these notable writers see fit to use contractions freely in their work:
But the magistrate was half blind and half childish, so he couldn’t reasonably be expected to discern what other people did. [Charles Dickens]
Berkeley doesn’t deny matter, then; he simply tells us what it consists of. [William James]
What was the good, after all, of being a woman if one didn’t keep fresh, and cram one’s life with all sorts of views and experiments? [Virginia Woolf]
… And there’s a barrel that I didn’t fill / Beside it, and there may be two or three / Apples I didn’t pick upon some bough. [Robert Frost]
There wasn’t a fat person to be seen. [Kurt Vonnegut, Cat's Cradle]
But couldn’t theatre dissolve the distinction between the truth of artifice and the truth of life? [Susan Sontag, Styles of Radical Will]