Comma: What It Is and How to Use It

Comma: What It Is and How to Use It


One of the most important punctuation marks is the ubiquitous comma (,). It is a necessary component of all advanced writing, as well as being a useful tool for delineating information. However, the comma is often improperly utilized; the mantra, “a comma goes where you would take a breath” does not quite capture what a comma really is and what the rules that govern its use are. Therefore, here is a brief primer on the role and function of commas in writing in English.


What is a Comma, Exactly?

According to the Purdue OWL, a comma is “a valuable, useful punctuation device because it separates the structural elements of sentences into manageable segments. The rules provided here are those found in traditional handbooks; however, in certain rhetorical contexts and for specific purposes, these rules may be broken.”


In short, commas separate parts of sentences; however, their uses are both varied and controversial.


Comma Rules and Examples

Here is a brief overview of the most important comma rules.


  • Independent clauses. Commas are used to separate independent clauses when they are separated by the FANBOYS conjunctions (for, and, nor, but, or, yet, so).
    • Example: “The boys threw the baseballs, so the girls caught the baseballs.”
  • Introductory material. Commas are used after text that is prior to the main independent clause.
    • Example: “For example, my dog ate my homework.”
  • Setting off content. When sentences include addenda couched inside the main idea, those details are separated before and after with commas.
    • Example: “The cat, or so I thought, was peaceful.”
  • Ideas in series. When ideas are combined, one after another, or in lists, commas should be used to separate the pieces of information. Typically, this only applies to lists of three or more words or clauses.
    • Example: “After I hit my brother, I felt mean, sad and ashamed.”
  • Between coordinate adjectives. When two or more adjectives are used to describe a noun, commas should be placed between the adjectives (though not before the noun).
    • Example: “The big, angry, mean giant tried to eat King Arthur.”
  • Before quotations. When including a quotation that is not directly integrated into the surrounding text, use a comma prior to the open quote.
    • Example: “The frog was talking to the toad. The frog said, ‘You are my best friend.’”
  • Commas are used at the ends of sentences to indicate contrasting clauses or elements to indicate distinct shifts.
    • Example: “To the others, Tarzan seemed like strange, almost ape-like.”
  • Conjoining free modifiers. Commas are used when a free modifier refers to something from earlier in the sentence.
    • Example: “Angus watched the ship come in, joyously excited.”
  • Geographical names, dates, addresses, titles. When referencing geographical names, dates, addresses or personal titles are mentioned in a sentence, commas are used to set off these specific pieces of information. The main exception is month-year pairs (ex, June 1996).
    • Example: “Humblebert Engledinck, MD, is a practicing physician in the area.”
  • Use commas to avoid confusion in sentences.
    • Example: “To Jesus, Judas was both a friend and betrayer.”


A Comma Conundrum: The Oxford Comma

One of the most puzzling issues in contemporary comma discourses surrounds the Oxford, or serial, comma. The Oxford comma is a comma that comes prior to the “and” in a list. For example, a list that includes the Oxford comma looks like this: “At the store today, I had to buy ham, meat, and eggs.”


Two of the major stylebooks – guides to English grammar and use – are the AP (Associated Press) and Chicago Manuals. The two guides hold completely contradictory views, but for the same reason: to prevent misreading.


Unless you are writing for a specific client who demands a certain choice, most writers make their own personal decisions on whether to use the Oxford comma.


Even though commas are a complicated subject, these are some of the basic rules that can let you start writing with the best grammar possible.


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