5 Common Grammar Mistakes in Academic English

by Emily Herring, Harvard College Writing Center English Grammar and Language Tutor

#1: ARTICLES (the/a)

I found a cat. = I found any cat.
I found the cat. = I found a specific cat.
I found cats. = I found a general group of cats.

General rule: Use “a” for an unknown object; “the” for a specific, previously discussed object;
and no article for an abstract object or general concept.


I found the student’s book. = I found a book that belongs to one student.
I found the students’ book. = I found a book that belongs to many students.
I found the students’. = INCORRECT
General rule: Use ’s to indicate one person’s possession of an object and s’ to indicate a group’s possession of an object.
*The use of an apostrophe to indicate a plural is becoming widespread on social media platforms but is incorrect*


The repairs that are occurring on the metro prevent a large portion of the population from accessing the city.
General rule: Make sure that the proper verb form (“prevent”) accompanies the subject of the sentence (“repairs”).

The report was written by scientists. > The scientists wrote the report. The presentation was given by the student. > The student gave the presentation.
General rule: While passive voice is not grammatically incorrect, it is better to use active voice to make your prose clearer and shorter!


I lived in Boston for 3 years. > I no longer live in Boston.
I have lived in Boston for 3 years. > I still live in Boston.
General rule: Consider the time frame in which you are writing. The second example is more appropriate if you are writing in the present tense.

Stop splicing those commas!

by Raymond DeLuca, English Grammar and Language Tutor

The comma splice is a common mistake that I often find in student writing. It is, by no means, a catastrophic mistake, but it tells me that the writer is still trying to figure out what to do with commas, which play a really, really important role in English writing.  Just in these two sentences, I’ve already used five commas—now six! So, what is a comma splice?

To “splice” something means to unite it or to join it together with something else. When you connect two independent sentences with a comma instead of a period, a semicolon, or a coordinating conjunction (more on all that in a future post) that is called a comma splice.


I love my Expos class, writing isn’t so bad.

This sentence is written incorrectly. The comma in between “class” and “writing” is splicing together two separate sentences. Commas do a lot of different things in written English, but they cannot (on their own) connect two sentences. How could we re-write the above example to make it correct? Here are a few solutions:

Solution #1: I love my Expos class. Writing isn’t so bad.

Solution: #2: I love my Expos class; writing isn’t so bad.

Solution #3: I love my Expos class, and writing isn’t so bad.

The simplest way to fix the comma splice is Solution #1. A period, not a comma, is what we need to separate two sentences: I love dogs. I love cats. Dogs love me. Cats could care less about me.

Let these short sentences stand and breathe on their own. For those of you who are a bit confused by Solution #2 and/or Solution #3, don’t worry. There’ll be a future blog post about that soon. For now, remember that a period is the easiest way to fix a comma splice.

It should be said that some writers intentionally use comma splices for stylistic purposes. A comma splice can convey causality, give a sentence an informal tone, or be used for dramatic effect. For example, writers tend to transcribe Julius Caesar’s famous phrase “Veni, vidi, vici” in English as “I came, I saw, I conquered,” not as “I came. I saw. I conquered.” It’s more impactful with the comma splices, isn’t it? But save that sort of splicing for the pros. You need to learn the rules before you can start breaking them.