5 of the Most Common Grammar Mistakes and How to Avoid Them

5 of the Most Common Grammar Mistakes and How to Avoid Them
Updated on 10 July 2015

Grammar isn’t just the domain of high-minded intellectuals holding court in an ivory tower, nor is it a sadist creation designed to make you feel frustrated and confused. It’s a system and structure that’s genuinely in existence to help us communicate more clearly—to help us better understand each other and derive meaning from the things we say and write.

That’s why it’s so important to take notice of grammatical mistakes and figure out what you need to do to correct them. To start you on your way, here’s a snapshot of five of the most common grammatical errors and some advice about how to make sure you’re never in the wrong again.

1 It’s and its

If there were a grammar mistake hall of fame, it’s/its would have New York Yankees status. Nearly everyone who’s ever put pen to paper has incorrectly used one of the two forms, but there’s an easy way to make sure you never make this error ever again.

It’s is a contraction that means ‘it is’ or ‘it has,’ whereas its is a possessive pronoun. When deciding which form to use, simply try to insert ‘it is’ or ‘it has’ where you were planning to insert your it’s/its. If the sentence reads correctly, you can use it’s. If it doesn’t, use its.


It’s always a beautiful day in Mr. Rogers’s neighborhood.

Donald Trump’s dog loved its new Prada poncho.

2 There, their, and they’re

Similarly, this deadly homophone trinity has plagued writers since before the time of, well, the Black Plague. As is the case with it’s, they’re is a contraction that means ‘they are’. On the other hand, their is a possessive pronoun, and there functions as either an introductory pronoun or as an adverb.

It’s slightly more complicated to decide which form to use, but you can still apply some basic rules to help you choose. If you can insert ‘they are’ where you would insert your their/they’re/there, then you can use they’re. If not, try to figure out if the their/they’re/there is being used to indicate belonging. If this is the case, then their is appropriate. Alternatively, if you need to introduce the subject of a sentence or denote place, there is the best option—you can remember this by reminding yourself that there has ‘here’ inside of it.


Frank and Joe Hardy couldn’t believe their luck. The missing evidence just materialized before their eyes, and they were able to solve the case of the missing butter dish.

They’re off to see the Wizard, the wonderful Wizard of Oz.

There was a knock at the door.

Don’t put the crib by the trash can; put it over there , in the corner of the room.

3 Subject-verb agreement

Failing to find that perfect, happy, peanut-butter-and-jelly kind of agreement between a subject and a verb is the kind of error that translates into slow, Medieval-style torture for copyeditors across the country. To make sure we keep these noble grammarians pain-free, it’s essential to remember that subjects and verbs must always align in number. That means that a singular subject goes with a singular verb, and plural subjects go with plural verbs.

This is easy enough to get right when a subject and a verb are close to each other, but it can get more complicated when prepositional phrases or complicated clauses create distance between the two. To avoid a mistake in the latter case, take a moment and underline your subject or subjects. Then decide whether a singular or plural verb is appropriate.


The Silicon Valley techies are super excited for their mixer with the Miss America contestants.

The use of calculators is prohibited on the math exam.

Mickey , who looked dashing in his giant yellow shoes, and Minnie , who looked equally fetching in her polka-dot hair bow, were the guests of honor at the cheese gala.

4 Comma splices

The comma. This pesky little punctuation mark is linked to a countless number of grammatical mistakes, but hands down, the most common type of error it’s involved in is the notorious comma splice. For those unfamiliar with this thorn in the editorial backside, a comma splice is a term used to describe the linking of two independent clauses (phrases that have both a subject and a verb) with a comma.

Incorrect examples:

Jay-Z confided in Beyoncé, he told her he wanted to put a ring on it.

He hit the jackpot at Las Vegas, all of the money on the table was his for the taking.

In both cases above, the independent clauses on either side of the commas could stand alone as complete sentences. Thus, the writer must instead decide whether to use a period, semicolon, or dash based on context and style. The only time a comma would be relevant is if the two phrases were linked by a coordinating conjunction (and, but, or, yet, so, nor, for).

To avoid comma splices, simply make sure one of the above conjunctions is present and accounted for and that it separates two clauses that both have subjects and verbs.

Correct examples:

Jay-Z confided in Beyoncé, and he told her he wanted to put a ring on it.

He hit the jackpot at Las Vegas, so all of the money on the table was his for the taking.

5 Apostrophes

Apart from commas, apostrophes seem to cause the most punctuation-related grammatical confusion. As we’ve pointed out in our Grammarly Handbook, the incredibly powerful little glyph “can change pronouns to verbs, tell you who owns what, replace a small handful of letters, and make plurals [of lowercase and uppercase letters].” Though, before you go out wielding the divisive mark, it’s essential to know how to use it.

The most important question to ask yourself when inserting an apostrophe is, “am I making a contraction or making a noun possessive?” If the answer is yes, then you can use the apostrophe. Keep in mind, an apostrophe is NOT used to make something plural ninety-nine percent of the time. The only exception to this rule is, as mentioned above, when you need to use an apostrophe to make a letter plural.


I removed the banana’s peel to get to the good bit.

I can’t believe global warming’s effect on the average summer temperature.

Mind your p’s and q’s when speaking to the Queen of England.

Is there a mistake you make all the time that you need help with? Let us know in the comment section below or via our Facebook or Twitter feeds, and we’ll try to explain it in a blog post.

Author Bio: Stephanie Katz is a San Francisco–based freelance writer who, contrary to the way it may seem, won’t correct your grammar over beers, coffees, or any other normal life interaction. She tells stories about health, history, travel, and more, and can be contacted via email at stekatz@gmail.com.

Grammarly is a must-have
writing app
that makes sure everything you type
is clear, effective, and mistake-free.
Get Grammarly It's free
Trending Posts