Avoiding Common Grammar Mistakes

This post originally appeared on the George Mason University English Writing Guide site. While it’s intended for use by students of that University who are following a specific essay-writing curriculum, the common errors it lists will be helpful for anyone who’s doing a self-editing pass.


By this point you’re done composing your essay. You’ve written an introduction and conclusion, incorporated transitions, and you’ve made use of textual evidence to support your argument. But you’re not done with your first draft yet—you still need to comb through what you’ve written to make sure that you don’t have any grammar mistakes.


Common grammar mistakes not only get in the way of your reader’s ability to understand your argument, but they can also undermine your credibility in the reader’s eyes. We’ve compiled here a list of common grammar mistakes that came up most often for professors in the English Department.

Common Pet Peeves for Teachers

Grammar Errors

  • Comma splices—A comma splice is where a comma is used to join two independent clauses which should be separated by a period. An independent clause can stand on its own as a sentence. Do not simply use a comma everywhere a reader would pause.
  • Subject/pronoun disagreement—There are two types of subject/pronoun disagreement, shifts in number and shifts in person.

    • Shifts in number—This phrase means the shifting between singular and plural in the same sentence. Be consistent.
    • Shifts in person—This error occurs when the person shifts within the sentence from first to second person, from second to third person, etc.
  • Its/it’s—"Its" is the possessive form of "it." "It’s" is the contraction of "it is." They are not interchangeable.
  • Mis-use and abuse of semicolons—Semicolons are used to separate two related independent clauses or to separate items in a list that contains commas. Do not abuse semicolons by using them often. They are best used sparingly.
  • Dropped commas around clauses—Place commas around words, phrases, or clauses that interrupt a sentence. Do not use commas around restrictive clauses, which provide essential information about the subject of the sentence.

    • Interrupting clause—This clause or phrase interrupts a sentence, such as "however." Place a comma on either side of the interrupting clause.
    • Restrictive clause—This clause or phrase provides essential information about the subject of the sentence. Without this clause or phrase, the meaning of the sentence changes.
    • Non-restrictive clause—This clause or phrase modifies the subject of the sentence but does not change the meaning of the sentence if left out.
  • "Naked this"—Always include a referent with "this," such as "this sentence" or "this rule." With no referent, "this" can confuse the reader.


Read the rest of the post on the George Mason University English Writing Guide.