Top 10 Grammar Mistakes According to Microsoft and Grammarly

Reading Time: 5 minutes

Microsoft and Grammarly have released lists of what they claim are the top ten grammar mistakes. Grammarly’s ads tout its ability to identify mistakes in your writing.  And Microsoft feels its Word Editor tool is robust.  But can you rely on the Editor function to find your errors?

And how well do the two tools match up?

Not well at all.  While Microsoft claims the number one mistake is too many white spaces between words, Grammarly claims the number one mistake is spelling.  The more you look, the more it becomes apparent the two don’t agree on much of anything.

Leaving too many white spaces between words1Spelling mistakes
Missing a comma  2Run-on Sentences (no comma before a coordinating conjunction)
Missing a comma after an introductory phrase  3Sentence fragments
Missing a hyphen  4No commas after an introductory phrase
Incorrect subject-verb agreement  5Wordiness
Incorrect capitalization  6Comma splices
Mixing up possessive and plural forms  7Comma misuse
Incorrect agreement with noun phrases  8No commas around interrupters
Commonly Confused Words  9Squinting modifiers
Incorrect Verb Form After Auxiliary verb  10Subject-verb agreement

1.      Spacing versus Spelling

First, spacing is not a grammatical mistake but a convention.  People debate whether there should be one after a period or two, but comparad to spelling, spacing after periods is minor.   Not only that, as I type this in Word, it underlines comparad but completely ignores my inconsistent spacing between sentences.

And although spelling has gotten worse because of autocorrect, most spelling errors today are centered around misused words, which Word lists as #9.

2.      Missing a Comma versus Run-on Sentences

Commas are important for meaning; however, run-on sentences are far more distracting.  Compare

  • Before we went to the store I stopped at the ATM.


  • We went to the store I stopped at the ATM.

Before we went to the store is a dependent clause before an independent clause; therefore, a comma is required before store.  However, that mistake is far less distracting than the second.

And as I type this, Word doesn’t correct either one.  It kept capitalizing “with,” however.  ☹


3.      Missing a Comma After Introductory Phrase versus Sentence Fragments

Word picks up on comma mistakes frequently.  Missing a comma can include everything from no comma after a conjunctive adverb (however, I forgot that one) to forgetting commas around a non-restrictive clause (Coach Davis, who also teaches Math, has won 7 games this season.)

However, what does Microsoft mean by introductory phrase?  Is it this:

  • In the morning we had breakfast.


  • After we had breakfast, we went for a swim.

In the morning is a phrase while After we had breakfast is a dependent clause.  A comma after a short introductory phrase is optional, but a comma after a dependent clause is not.

Grammarly is right again that sentence fragments require more attention.

  • We arrived at the store.  Only to find it closed.

4.      Missing a Hyphen versus No Commas After an Introductory Phrase

So now Microsoft wants to wade into the hyphen wars.  Should twenty-three be hyphenated?  How about 6-inches?  How about my 4-year-old?  A lack of consistency and constantly changing rules about hyphenation cause this mistake.

Grammarly finally addresses commas; however, I guess they are also putting phrases and clauses in that category.

5.      Incorrect Subject-Verb Agreement versus Wordiness

Score a point for Word.  Subject-Verb agreement, especially if there’s a long phrase between the subject and the verb, are a common mistake.  (However, Word did not catch it in this sentence, but Grammarly did).

Sorry, Grammarly–wordiness is annoying and a way for students to pad their essays, but it has nothing to do with grammar.

6.      Incorrect Capitalization versus Comma Splices

Thanks to autocorrect, incorrect capitalization is rarely a problem unless a writer purposefully keeps a word in lower case and Word corrects it.

Comma Splices are the bane of English teachers’ existence.  When you join two independent clauses with a conjunction, put the comma before the conjunction. 

On the one hand, it doesn’t seem complicated.  But people who use commas instinctually must learn the difference between clauses and phrases, dependent and independent clauses, and conjunctions.

It can be a lot to unpack, and teachers find themselves unpacking those concepts again and again.

7.      Mixing up Possessive and Plural Forms versus Comma Misuse

Both are common problems, and now Grammarly is beginning to repeat itself.  Comma misuse could mean many things.  Grammarly seems to be saying that writers make lots of mistakes with commas. 

They aren’t wrong.

Word points out a frequent grammatical error that doesn’t even make it into Grammarly’s top ten.  This mistake happens when a writer is unclear about what to do with apostrophes and plural words.

In the sentence

  • My sisters kitten is cute.

An apostrophe is clearly needed.

  • My sister’s kitten is cute.

But sentences where the noun is plural are more confusing:

  • My brothers wives went shopping yesterday.

Here the speaker must have more than one brother, and the comma should come after the ‘s.’ 

  • My brothers’ wives went shopping yesterday.

Even I have to stop myself from adding an extra ‘s’ – My brothers’s wives—but thankfully, Word alerts me to the mistake.

8.      Incorrect Agreement with Noun Phrases versus No Commas Around Interrupters

Microsoft gives this example:

  • I would like to buy this apples.

I find it difficult to believe this mistake is that common.

9.      Commonly Confused Words versus Squinting Modifiers

This juxtaposition is interesting.  Commonly confused words is an obvious mistake and happens to often because the writer didn’t proofread carefully—or made the mistake on purpose.

Squinting modifiers, on the other hand, is a subtle error.  When a word could modify either the Word before or after it, it is “squinting.”  The reader is “squinting” to figure out what is being modified. 

This is Grammarly’s example sentence:

  • Students who study rarely get bad grades.

Grammarly suggests the modifier (rarely) should be placed before study.

  • Students who rarely study get bad grades.

Although this is technically correct, practically both sentences say the same thing: if you don’t study, you will get bad grades.

10. Incorrect Verb Form versus Subject Verb Agreement

Microsoft gives this example for an incorrect verb form.

They had ate when we came.

Obviously, this is a mistake.  However, this mistake doesn’t occur nearly as much as subject-verb agreement.  And Word has a hard time with this mistake. 

For example, it thinks the following is incorrect:

  • Commonly confused words is an obvious mistake

But the following is correct, according to Word.

  • an obvious mistake is commonly confused words

Word does know that the verb should be singular in these sentences:

  • The problem is rotting timbers.
  • Rotting timbers is the problem.

Bottom Line

Word’s Editor function can be helpful.  I tend to use contractions frequently, and I use the tool to help me find them.  It also identifies some wordiness and obvious spelling.  I use the readability stats for sentence length, readability, and passive voice.

As you can see, Grammarly gave me far more and better feedback than Word.

That doesn’t mean Grammarly is perfect.

Ultimately, I am going to rely on Grammarly to catch my mistakes.

An update–I have cancelled my subscription to Grammarly and now rely on Quillbot instead. I explain why in What is Quillbot?

Click here to try Quillbot for Free!
Microsoft's Word Readability Statistics
Microsoft and Grammarly: Grammarly wins!

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