Be Your Own Proofreader: 11 Errors to Avoid

Keep your writing polished — and save your proofreader’s red pen — by eliminating these 11 common errors.*

1. it’s vs. its
This often confuses people because we usually add an apostrophe “s” to indicate possession: the boy’s bicycle, the frogs’ legs, the baby’s bottle.

Not with “it,” though. It’s (with apostrophe) always means “it is.”

“Its” (no apostrophe) indicates possession, like his, hers, and its.

So: It’s better for your car if you change its oil every 5,000 miles.

2. you’re vs. your

Similar to it’s and its, misuse of you’re and your shows up far too often.

You’re always means “you are.”

Your indicates possession.

So: You’re welcome to bring your own bottle of wine to the restaurant.

3. that vs. which

Even good writers get confused by this one. (Is it “I like the beer that won the taste test”?  Or “I like the beer which won the taste test”? Or doesn’t it matter?)

It matters. I think people often choose “which” over “that” because they think it sounds fancier or more proper.

Here’s an easy way to remember: If you want to use “which” in this way, you need to add a comma before it. If the sentence still makes sense, “which” is the way to go.

Let’s try it with the earlier example.

“I like the beer, which won the taste test.” probably isn’t what you really mean. By using the comma and which, you are saying you like the beer (in general) and, oh, by the way, it won the taste test. The whole sentence is just awkward.

You probably meant to say you like a specific beer.

So:  I like the beer that won the taste test.

If you remember “which” is used to set something apart in a sentence and call attention to it, you’ll use it correctly.

So: The beer that won the taste test, which was conducted by master brewers, was also my favorite.

4. Overuse of “that”

Speaking of “that,” you can often eliminate it and your sentence will still make perfect sense.

So: I knew that I was wrong about that story, but only because the information that she gave me was wrong.

5. i.e., vs e.g.,

“i.e.,” is short for the Latin term id est, meaning “that is.” It should always have a comma after it. Add a comma before unless you’re using parentheses.

So: The milk was bad, i.e., rancid, so I threw it away.
Or: The milk was bad (i.e., rancid), so I threw it away.

“e.g.,”is short for the Latin term exempli gratia, meaning “for example.” The same comma rules apply.

So: Experiment with different cheeses (e.g., fontina, asiago, gorgonzola) instead of always reaching for the parmesan.

6. One word or two?
Many words you might think are two words or hyphenated are really one.  Here are some examples:

twofold, threefold

On the flip side, words you may think are one word are not:

health care
life cycle
road map

I wish I had an easy way to know which is which. Truth is, I frequently consult the dictionary on this topic.

7. One space after end punctuation

Many of us were taught to type two spaces between sentences and after colons. This is a carry-over from typewriter days, when fonts were not proportionally spaced. Each character took up the same space when typed, so using two spaces between sentences offered a break in the monotony and made for easier reading.

Fonts today are proportionally spaced, meaning a w is not the same width as an i, is not the same width as a 4, and so on. Two spaces are no longer needed.

Don’t believe me? Pick up any book or magazine. It uses only one space between sentences and after colons, and you can read it just fine.

It may take a bit to break yourself of the two-space habit, but it’s not that difficult. I have gone from typing two spaces (since learning to type in high school), to one space (at work 10 years later when I learned it was correct), back to two spaces (to meet my next employer’s incorrect house style), and finally back to one space. (I’ll never switch again.)

8. Apostrophes — using and “aiming”

The computer takes away any effort in typing apostrophes in contractions like can’t and won’t and it’s. Notice the apostrophe looks something like the number 9 on serif fonts like this one, and slants up and to the right on sans serif fonts (like Arial).

This same upward-right slant is the proper apostrophe to use whenever it takes the place of letters or numbers.

So: In the early ’90s, she was working as a waitress in a cocktail bar.
Or: The store encouraged us to “mix ’n’ match” sale items.

In some word processing programs, when you type a date like ’80s or ’90s, the computer will insert a single quotation mark facing the wrong way. Just position your cursor after that quote mark and type an apostrophe; it will be facing the proper way and you can just delete the wrong-facing one.

Oh, and remember not to add an apostrophe before the “s” when writing dates such as the 1880s or 1960s.

So: I was in my early 30s before I realized I had lived in the 1880s in a previous life.

Finally, if your apostrophes and quotation marks are straight up and down, you’re really typing foot and inch marks. Apostrophes and quotes should always be slanted or “curly.”

9. Consistency in using serial commas (or not)

A serial comma is the comma before “and” or “or” in a series.

So: He bought clams, shrimp, and saffron for the paella.

Depending on your “house style,” you may or may not use serial commas. If not, the sentence would be: He bought clams, shrimp and saffron for his paella.

My preference is to use serial commas, but some of my clients don’t. My job is to make sure they are consistent, either with or without. That’s your goal, too.

Note that even if you don’t normally use serial commas, complex sentences sometimes beg for them for easier reading. It’s okay to use them in these cases and eliminate them elsewhere in the same document.

So: His expertise includes a variety of electrical inventions, including those concerning consumer products, medical devices, software, wireless and wireline telephony and circuitry, and digital signal processing.

10. Forgetting a necessary “and”

Do you see anything wrong with this sentence?

We are experts at repairing broken drains, leaky faucets, and installing new plumbing.

It’s actually missing an “and.”

What the writer meant to say was that the company is expert at repairing broken drains and leaky faucets. It’s also expert at installing new plumbing.

So: We are experts at repairing broken drains and leaky faucets, and installing new plumbing.

11. Punctuation inside quotes (or not)

Basically, commas and periods go inside quotation marks, question marks sometimes go inside and sometimes outside, and all other punctuation goes outside.

So: We think our special recipe has just a hint of “magic.”
Is this paint “scarlet,” “ruby,” or “crimson”?
When he said, “Who cares?” I knew it was time to stop shopping.

Three qualities make up the Acme “difference”: know-how, speed, and price.
My favorite TV show is “The Office”; I never miss it.

These are just a few common errors I encounter when proofreading and editing. For an extremely helpful and entertaining refresher on many more aspects of grammar and good writing (and a great reference for your shelf), check out:

Woe Is I: The Grammarphobe’s Guide to Better English in Plain English
by Patricia T. O’Conner

And for a British twist (even Americans will enjoy):

Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation
by Lynne Truss

Both are lively enough to read (willingly) on the plane, train, or over lunch and comprehensive enough to become a trusted resource.


Everyone needs an editor.
~Tim Foote
commenting in
Time magazine on the fact that
Hitler’s original title for
Mein Kampf was
Four-and-a-Half Years of Struggle against Lies, Stupidity, and Cowardice

* Note: These tips apply to American English — British English may handle some of them differently.


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