Common Punctuation Mistakes

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.

  • quick-rising
  • bricks-and-mortar
  • B-to-B
  • out-of-the-ordinary

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.

  • 1966–69
  • 20–30 minutes
  • A–D classes
  • Maryland–North Carolina

An em-dash (aka M-Dash, for the same reasons) 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 — she usually just calls herself “the Doctor” — mayhem and mischief usually follow.
  • He’s also called the madman in a blue box — the TARDIS, his spaceship.

hyphenating ages

  • 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

parentheses, nested         

A parenthetical inside another parenthetical uses square brackets.

  • Choice of classes (Monday [pending instructor availability], Tuesday, or Wednesday)


See “The Almighty Apostrophe”

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 mostly 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