Top Grammatical Errors That Damage Your Credibility


  • Basic punctuation and sentence structure rules are the foundation of your authority as a content creator.
  • Content that’s rife with grammatical errors can damage your credibility and ultimately lowers your ROI.
  • Beyond the basics, avoiding tricky errors like misplaced modifiers and parallelism can take your content writing “grade” from passing to A+.
  • The best SEO content writing doesn’t blindly adhere to grammar rules. Know the rules before you break them, but when in doubt, go with what sounds the most natural and engaging.

Ever read a piece of online content and thought, “Was the editor on vacation when this got published?” Mistakes are natural, even for the most experienced SEO content writers. But content that’s rife with punctuation and spelling errors ultimately damages the credibility of not only the writer, but also the platform on which the content has been published.

We get that not everyone loves grammar. It can be difficult, confusing, and above all, boring. That’s why we’ve done the hard work for you by putting together ten grammatical errors and issues we see all the time that can have a negative affect on your ROI – and brand presence.

Scroll down for six basic grammatical errors and four advanced ones to address in your content writing ASAP.

The basics

1. Incorrect apostrophe use

The general rule for apostrophes is to use them in possessive nouns and to replace missing letters in contractions.

Let’s break that down

Plural vs. possessive nouns

Apostrophes are for possessive nouns, not plural nouns. That means an apostrophe should go between whatever singular noun has possession and “s.” See the example below.

Correct: The dog’s collar is red.

In this case, there is one dog, and it has ownership of the collar.

Incorrect: I’ll go feed the dog’s.

If the writer is talking about a group of dogs, no apostrophe is necessary.

But what about plural possessives? For example, a group of dogs might have ownership of a toy, or a group of toys. In that case, the apostrophe goes after the “s” of the plural. See below:

Correct: The dogs’ new toys are in the car.

Incorrect: The dogs’s new toys are in the car.


Another common use of apostrophes is to replace missing letters in contractions. Examples include can’t, won’t, haven’t, isn’t, aren’t – the list goes on.

Special cases and exceptions

It’s vs. Its – The pronoun “it” behaves differently than other possessive nouns. When “it” has ownership, it does not need an apostrophe. However, when “it” is part of a contraction, it does. See below:

Correct: The dog chases its tail.

Incorrect: The dog looks at it’s reflection in the mirror.

Correct: It’s a warm day.

Incorrect: Its no big deal.

Nouns that aren’t nouns – Occasionally, we use nouns that aren’t technically words. Lower-case letters are a great example. In that case, use apostrophes to mark plurals.

Example: Make sure to cross your t’s and dot your i’s.

2. Missing (or misuse of) commas

Commas can be tricky. Many people think of commas as pauses, but in natural conversation, we often pause even when no comma is needed grammatically.

Because of this, comma errors are some of the most common to crop up in content we see. A few here and there are no big deal – no one’s perfect! And if your writing is more conversational, some flexible comma use may be appropriate for your tone.

Still, it’s important to brush up on the rules before you break them.

In general, use commas to…

…separate items in a list.

Example: I’m going to the store for milk, eggs, and cheese.

There’s some debate over what’s called the Oxford comma, which is the last comma in a list (before the word “and”). This comma is not technically necessary.

The above example, for instance, would work if re-written as: I’m going to the store for milk, eggs and cheese. However, many writers and editors argue that the Oxford comma improves clarity overall.

The most important thing is that you remain consistent. If you use the Oxford comma in your writing, make sure it’s used in every list, not just some of them.

…make compound sentences with conjunctions.

Example: The sun is out, but it’s quite cold.

…separate a dependent clause, modifying phrase, or interjection from the rest of the sentence.

Example: I love the weather in Southern California, although the air is dry.

Example: My sister, who lives on the East Coast, always likes visiting.

Example: My mother, however, prefers rainy climates.

3. Subject-verb and noun agreement errors

Make sure singular subjects go with singular verbs and plural subjects go with plural verbs. This can get tricky the more modifying or interjectory phrases your sentence contains.

Correct: Your car, which needs new tires, nevertheless drives well.

Incorrect: Dogs with thick fur needs frequent grooming.

In the above example, the subject of the sentence is “dogs,” not “fur.” Since “dogs” is plural, the verb should actually be “need.”

Be careful with nouns like “each” and “every,” too. These nouns are technically singular. See how the following examples work:

Correct: Each dog has received a new bone.

Incorrect: Each of the dogs have received a new bone.

Above, even though “each of the dogs” ends with the plural “dogs,” the subject is still “each” – a singular noun.

Correct: Everyone is present.

Incorrect: Everyone is in their seats.

In the second example, the singular noun “everyone” should go with another singular phrase, like “his or her seat.” The singular verb “is” (as opposed to “are”) gives you a hint.

4. Incorrect word form

This type of mistake is easy to make because it can take so many forms. See a couple of common errors below.

Compound modifiers – One example of this we see all the time is “every day” vs. “everyday.” The word “everyday” is an adjective, to be used before a noun. The phrase “every day” is a modifying phrase that comes after whatever it’s modifying.

Correct: Your everyday wardrobe should be comfortable and practical.

Incorrect: I ride the bus to work everyday.

Correct: The sun rises in the east every day.

Incorrect: Please describe your every day routine.

In the above example, “everyday” is a word unto itself, but some compound modifiers require hyphens. See the example below.

Correct: We offer video on demand.

Incorrect: Our on demand video service is popular with customers.

Correct: Check out our on-demand video service.

Incorrect: With our service, you can watch video on-demand.

Verbs turned nouns – Sometimes, a verb phrase can change form and become a noun. When this happens, the noun form is usually hyphenated or becomes a new compound word.

Correct: Make sure to back up your files regularly.

Incorrect: We offer free file back ups.

Correct: You should perform regular backups to prevent file loss.

Incorrect: Always backup your files to prevent loss or damage.

5. That vs. Who

This is another rule that’s so simple, it’s easy to forget. That makes it all the more obvious when writers mess it up.

We’ll make it short and sweet: “That” goes with objects, while “who” goes with people. Observe:

Correct: The candidate who wins the most votes will become the next class president.

Incorrect: The student that gets the highest GPA will be named valedictorian.

6. Spelling and idiom errors

Okay, so it’s impossible for any one person to know how to spell every word and idiom in the English language. The best advice we can give content writers is to always have a second pair of eyes look over content before publication…

…and read, read, read! Reading a variety of content, from fiction to quality online journalism, gives you the best grammar education you can get.

If you need some quick notes, though, check out our list below.

  • Affect vs. Effect – Usually, “affect” is a verb. “Effect” is a noun. However, you can “effect change,” or have a “subdued affect.” We know… it’s confusing.
  • It’s “For all intents and purposes,” not “For all intensive purposes.”
  • You can have “a lot” of money, but never “alot” of it.

Advanced tips

7. Misplaced modifiers

Because this mistake is so tricky to detect, it can slip easily past even a keen reader’s eye. Basically, make sure any modifying phrases are next to the nouns or pronouns they modify. See below:

Correct: A talented artist, Sarah won a grant to help fund her next project.

Incorrect: A fascinating debut novel, Jane Smith will publish the new book in July.

In the incorrect example, “A fascinating debut novel” describes “the new book,” not “Jane Smith.”

8. Parallelism errors in lists

Whether in a sentence or in bullet points, lists should contain items with parallel structure. This can mean listing all action phrases, or all infinitive verbs (like “to read”), but not a mix.

Correct: My advice for scoring well is to study regularly, eat well, and get a good night of sleep.

Incorrect: She suggests adding lots of salt, bring the water to a boil, and to cook for twenty minutes.

9. Incorrect comparison word

This is one of the sneakiest grammatical errors to catch because we usually ignore these rules in informal conversation. You’ve probably heard news anchors, radio hosts, and even teachers say things like, “There are less people here than I expected,” without skipping a beat. In writing, however, it can be glaringly obvious to the trained eye.

“Less” and “much” describe amounts you can’t count in units, such as “money” or “water.” “Fewer” and “many” compare numbers of individual things, such as “people” or “dollars.”

Correct: The white chicken lays fewer eggs than the red chicken.

Incorrect: I always eat less eggs than my brother.

Correct: There are so many people here today.

Incorrect: There’s too much clothes in the hamper.

10. Grade school rules

We all learned at least some grammar rules in grade school. Phrases like “Never start a sentence with because” have become mottos burned in some of our memories – but we don’t always remember the reasons for those rules.

This leads to oversimplifications that can make for awkward and stilted writing. We’ll break down some of those oversimplified rules (and why you can and should break them) below.

Avoiding contractions – Many people are taught that contractions don’t belong in “formal” writing (reports, essays, and articles). But much of the content we write – and enjoy reading – in our daily lives is more conversational in nature. Contractions help smooth out the tone of this kind of writing, and actually lend the writing a stronger sense of confidence and authority.

Compare the two sentences below. Which sounds more natural?

When it is hot out, there is nothing better than a day at the beach.

When it’s hot out, there’s nothing better than a day at the beach.

Take it from a professional content editor: Contractions are your friends!

Never starting sentences with “But,” “Because,” Etc. – This rule has its heart in the right place. It’s intended to prevent sentence fragments. Strictly speaking, “But I can’t attend” and “Because I said so” can’t stand alone as sentences because they start with words that make them dependent or subordinate to another part of the sentence.

However, much like contractions, these words can be used more flexibly in informal or conversational writing. While you shouldn’t abuse this flexibility, you can and should explore stylistic choices that may add humor or emphasis to an otherwise dry structure.

Check out the examples below.

Why is the painting so controversial? It’s controversial because it crosses boundaries.

Why is the painting so controversial? Because it crosses boundaries.

Most readers would probably agree that the second example is more direct and powerful, because it sets up a rhetorical question that’s answered clearly and concisely. The first example is technically correct, but it’s much less punchy.

Never ending sentences with prepositions – This is another well-meaning rule that gets broken in speech so often that it’s become somewhat more flexible in writing, too.

Let’s demonstrate some “proper” preposition use:

Correct: On which horse are you betting?

Incorrect: Which horse are you betting on?

The second sentence is technically incorrect. It also sounds way more normal and natural than the first sentence. While some sentences can be re-written to avoid the problem altogether, when in doubt, go with what sounds clearer and more conversational.

Remember, your goal for SEO content writing is to connect with readers through engaging content, not beat them over the head with your grammar expertise. (Unless you’re writing a blog called “Ten Grammatical Errors that Damage Your Credibility.”)

When in doubt, ask the experts

Not everyone gets as excited as we do about the finer points of prepositions and punctuation. We get it! That’s why it’s so important to have a trusted copy editor or two on your team. If not, don’t hesitate to reach out to the SEO content writing experts at Redefine Marketing Group. We’d love to answer your most complex, mind-numbing grammar questions. Seriously.

Author avatar
Stephanie Fehrmann
Stephanie was an SEO content writer before transitioning to a management role. As the co-founder and Head of Content at RMG, she oversees everything from the development of content strategies and content creation to day-to-day office operations. She graduated from Cal Poly Pomona with a degree in Journalism, and enjoys showing clients the power and versatility of content.
Share via
Copy link
Powered by Social Snap