A quick and handy list of common punctuation mistakes, and the correct versions:
dashes and hyphens
A hyphen is used to connect two or more words which need to be linked in a compound.
An en-dash (also sometimes spelled N-dash; the name comes from the mark being about the width of a capital N) is used to indicate a range.
- 20–30 minutes
- A–D classes
- Maryland–North Carolina
An em-dash (aka M-Dash) is used to set off an interrupter. If the interrupter is in the middle of sentence, use two em-dashes. I prefer to use spaces on either side, but that can change according to house style.
- When Doctor Who arrives — he usually just calls himself “the Doctor” — mayhem and mischief usually follow.
- He’s also called the madman in a blue box — the TARDIS, his spaceship.
- WRONG: The officer, 55-years-old, retired.
- RIGHT: The officer, 55 years old, retired.
- RIGHT: The 55-year-old officer retired.
hyphenating a range of numbers
- WRONG: A 2–3 minute speech
- RIGHT: A two- to three-minute speech (Note the space after the hyphen for the first item. This indicates that the hyphen belongs to “minute.” The full version of this phrase would be “two-minute to three-minute.” Spelling out the phrase removes the en dash and adds two hyphens.)
- WRONG: A 15–20 minute speech
- RIGHT: A 15- to 20-minute speech
- RIGHT: A nine- to 12-minute film (This is correct if you are following AP style, where numbers below 10 are always spelled out.)
- WRONG: one–seven minutes
- RIGHT: one to seven minutes
- WRONG: a list of three-to-four companies
- RIGHT: a list of three to four companies
- WRONG: between 15–20 percent
- RIGHT: between 15 and 20 percent
- RIGHT: from 15 to 20 percent
- RIGHT: between 6 and 8 percent
- WRONG: savings of six-to-seven percent
- WRONG: savings of 6-to-7 percent
- RIGHT: savings of 6 to 7 percent
A parenthetical inside another parenthetical uses square brackets.
- Choice of classes (Monday [pending instructor availability], Tuesday, or Wednesday)
quote marks as highlighters
Double quotes can be used appropriately as a highlight, but not single quotes. The only time single quotes are used as a highlight is if they are nested inside double quotes.
- RIGHT: the “Strongest Man in the World” competition
- WRONG: the ‘chain-stitching’ competition
- RIGHT: Janet said, “We’re proud to be hosting the ‘Strongest Man in the World’ competition this year.”
A much-abused punctuation mark. It is used to join two independent clauses, or full sentences. (It can also be used as a serial comma, which see below.)
- We went to the park, but soon left; it was too windy.
- Orange tabby cats are generally males; calico cats are generally females.
- Calico cats are generally females because color in cats is carried on the X chromosome; however, a rare genetic combination (XXY) can allow for a male calico.
If you use a comma instead of a semi-colon, this is called a comma splice, and it’s incorrect.
- RIGHT: Dogs bark; curiously, this one did not.
- WRONG: Dogs bark, curiously, this one did not.
serial comma (also known as the Oxford comma)
This is not a mistake as much as it is a style preference. I prefer it because I always like to err on the side of clarity, but it’s not wrong to skip it. So if you want to use it, it works like this:
Use the serial comma in a list of three or more items:
- James T. Kirk, Jean-Luc Picard, and Kathryn Janeway were all captains on Star Trek. Spock variously held the positions of first officer, science officer, captain, and diplomat.
Use a serial semi-colon if one or more of the items have commas:
- We had pancakes, waffles, and grits; three kinds of syrup; spam, spam, bacon, eggs, and spam; fresh fruit; orange juice, milk, and coffee; and Pepto-Bismol for a chaser.
Never use spaces on either side.
- RIGHT: either/or
- WRONG: either / or