13 Grammar Mistakes Writers Need to Avoid

We’ve got 13 of the most common (and annoying) grammar mistakes you should never make in your writing. This list of matchups between similar-but-not-quite-the-same words includes some guaranteed pain points. Take a look at the list and then give your book an edit to make sure you haven’t made any of these slip-ups!

A good editor may catch these for you. And a really good spell checker will help a lot too. But the more you know in the lead up, the more you catch while writing and self-editing.

Affect vs Effect

Grammar mistakes to avoid. Don't be like Fry. Know the difference between affect and effect.

Are you one of those people who writes “impact” because you aren’t quite sure whether you should be using “affect” or “effect”? Here’s a quick tip that will get you through most scenarios: affect is a verb – so one thing affects another – and effect is a noun. Just don’t get tripped up on “effecting change,” where you’ll use an “e” when you mean “to bring about” something.  Isn’t the English language fun (and sometimes aggravating)?

Insure vs Ensure

This one’s pretty simple. If you’re talking about insurance – as in limiting financial liability – use insure. Both start with an “i.” Ensure, when you’re guaranteeing something, is always with an “e.”

Then vs Than

Can proper grammar make you not sound like a crazy person?

Use then when something follows another thing: “I’ll learn these great grammar tips, and then I’ll proofread my books.” Than is used in comparisons: “Since I fixed all of my grammar mistakes, my book is selling better than it was before!”

I.e. vs E.g.

You might think these are interchangeable when you’re using an example, but there’s a very subtle difference between the two. I.e. mean “that is” or “in other words,” from the Latin “id est,” and you use it when you’re clarifying something. E.g., from the Latin “exempli gratia,” means “for example” and is used for just that – providing an example!

Fewer vs Less

Everything you know is a lie - the fast checkout line at your store uses incorrect grammar.

As a rule of thumb, you use fewer when you can count the subject in question individually and less when you can’t. So I can have fewer cups of water than you, but your cups might have less water in them than mine do. And yes, that means your grocery store sign is probably incorrect.

To vs Too (vs Two)

Last but not least, one that you probably know but can slip your mind when you’re writing. Most of the time you’ll use to when you’re talking about a verb or going toward a place, e.g. “I’m going to write” or “I went to the mall,” but when you mean to say “as well” or “also,” or something in excess, use too – “Sally went going to the mall, too, and she ate too much.” And just in case, two is always the number 2. Seems obvious, but you can never be too careful!

Your vs You’re

Your is possessive – as in, “That’s your dog.” You’re is a contraction of “you are.” Contractions are a common grammar mistake and your spellchecker may miss them, so be wary.

Grammar mistakes you shouldn't make - your, you're

Its vs It’s

Along the same lines, its is possessive, and it’s is a contraction of “it is” (or “it has”). Again, this is one grammar mistake that may slip through a spell checker.

Who’s vs Whose

Whose is possessive. Who’s is a contraction of “who is” or “who has.” Are you sensing a trend?

Avoid these grammar mistakes - there vs their vs they're

Their vs They’re vs There

Ready to throw in a third option? Their is possessive, and they’re is a contraction of “they are.” There will cover pretty much everything else, from “There goes the bus” to “Put that box over there” to “There aren’t any cookies here.” (Note: pirates may be inclined to throw in “thar.”)

Lose vs Loose

Don't make these grammar mistakes - lose, loose

This is best with a few examples. You can lose your dog if he gets loose from his leash. Your clothes will be loose if you lose a lot of weight. If you have loose change in your pocket, you might lose it. If all else fails, read your sentence aloud; if the word sounds like it ends with a ‘z’ then it’s lose; if it sounds like an ‘s’ then it’s loose.

Compliment vs Complement

The only difference is an ‘i’ and an ‘e’. So what’s the real difference? Compliment – with an ‘i’ – means you’re saying something nice to someone. Or, as an easy way to remember, “I am saying something nice to someone.” If you complement something, you’re adding to or improving it.

Farther vs Further

Farther refers to a physical distance – long distances are always far. “His house is farther away than mine.” Further is more figurative and means an extent of time or degree, as in “Tom wanted to talk further about the plan.” Farther and further are more readily accepted as being interchangeable than other examples in this list.


That’s it – for now! The English language is a wonderful, complex thing and even the best writers get tripped up from time to time. If you’ve got a favorite tip or a “this word or that one?” that seems to always get the best of you, share them in the comments!

7 thoughts on “13 Grammar Mistakes Writers Need to Avoid”

  1. In ‘affect vs effect’, you ask, ‘are you one of those people who writes…?’ The immediate antecedent of ‘who’ is ‘people’, therefore, the verb that comes after ‘who’ should be plural. Therefore the question should be, ‘are you one of those people who write…?’

  2. According to both the OED and the AP Style Book, the original sentence is correct; “one” is the noun so the verb must be singular,

  3. I really appreciated the information on I.e and E.g. That one has long plagued me. Thank you for sharing. Sorry. I know this is not a new tip.

  4. You should also address “loose” versus “lose.”
    Irks me to no end whenever I see loose for lose.

  5. Pingback: Finessing Your Manuscript: Common Mistakes to Avoid | Lulu Blog

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