In English, contractions are often used in informal speech and writing. (Minimize your use of contractions in formal documents, especially when clarity of terms is essential, such as in a contract or other legal document.)

Whether you are sending an email or text to a friend or associate or writing dialogue for an article or story, the use of slang, jargon, acronyms, abbreviations—and contractions—suggests a casualness that may or may not be appropriate, depending upon the impression you wish to make (e.g., “we’re colleagues and speak the same language”) and the context (e.g., you are quoting a source who said, “He’s a ne’er-do-well.”)

When forming a contraction, an apostrophe is often used in place of missing letters. Common contractions include:

I’m (I am)
you’re (you are)
he’ll (he will or he shall)
she’s (she is or she has)
we’d (we would or we had)
let’s (let us)
can’t (cannot)
shouldn’t (should not)
won’t (will not)
who’d (who had, who would)

It’s up to You

Compare: “Here is the report you asked for.”
with
“Here’s the report you wanted.”

The difference is slight, but the first sentence sounds more formal and “professional,” whereas the second is more casual. Neither is incorrect, but each will convey a different tone and sentiment.

(Note that if you are sending an email with an attachment, you might write “Here’s my bill” to a regular customer—but you would never say “Attached’s my bill” or “Attach’d is my bill.” Not all words are suitable for shortening!)

In dialogue, however, anything goes. Many people misuse language, so if you are creating a character who is from a particular region or country (or planet!), craft dialogue that reflects the character’s age, education, and situation. (A person who is stressed and rushed will speak and behave differently from a college professor delivering a lecture.)

“I ain’t goin’ and you cain’t make me.” [I am not going, and you cannot force me to go.]

“Who’da thought she’d go for him?” [Who would have thought she would be interested in him?]

As with the contractions noted earlier in this post, an apostrophe is used to indicate that letters are missing.

“Supposin’ I was ta ask you to the dance. What d’ya reckon your answer’d be?”

As slang and colloquial words and expressions catch on, alternative spellings become common:

“Well whaddya know! It worked.” [Well, what do you know? It worked!]

“Whatcha doin’?” [What are you doing?]

In all writing, avoid contractions if they are ambiguous and can be misread. As noted above, some contractions, such as I’d, can have more than one meaning (I would, I had). Don’t create extra work for your reader; if the meaning is not readily apparent, use the complete words.

I have previously written about the misuse of of when have is meant in contractions such as would’ve (I would have). Double contractions are especially messy and are best avoided. (I’d’ve for I would have)