If you are an editor, you know the power of comma. If you are not, ask editors about it; they will talk about it for days. Comma is the punctuation equivalent of Lord Krishna, taking various incarnations to decimate the demons of the reading and writing world, by thwarting the comprehension evil. To paraphrase Bhagavat Gita,
Whenever there is a decay of comprehensibility and growth of incongruity, to protect the reader, to destroy the wicked, the Comma manifests itself, through the pages.
Have you ever ruminated the roles a comma can play? To separate, to connect, to help emphasize, to introduce, to substitute, and what not. The comma is omnipotent and omnipresent. Comma is the Krishna of the world of words, the commander of us mortal editor Arjuns who wage an everyday Kurukshetra against the evil of loss-of-meaning, the Incomprehensibility.
Okay, before you think that I’m rambling, I’ll tell you why.
Let’s begin with the simplest: The primary use of commas is in lists, with an option to use the serial comma a.k.a. the Oxford comma.
Commas are used to separate independent clauses with coordinating conjunctions, to separate parenthetical phrases or clauses, and to separate a word or phrase for emphasis.
Commas are used to introduce as after introductory phrases or to introduce other elements, such as equations and quotations.
Commas are used to leave some trailing thoughts, giving the reader some more food for thought.
Commas can do so many other errands: these errands are so very mechanistic, not warranting a place here. For example, they are added after abbreviations such as “e.g.” in American English, separate the date and the year – again, in American English – and so on.
But what is more alluring to me is providing us with the most sophisticated punctuation weaponry, commandeering the editing war with ease.
Did you notice that for each of the roles listed above, there are alternative punctuation marks? Come, let’s explore.
One most frequent appearance of commas is to separate items in a list. What if things get complicated? What if the items of the list themselves are lists? What if all or some of the list items already have commas? Will it not look like a comma litter? If only there is a better way…
There is. In the form of a semicolon. Semicolons separate list items if the list items either have internal commas or are lists within lists. They easily stand in the shoes of commas. Oh, yeah, there is that serial semicolon, too.
A second instance where comma is most needed is to separate parenthetical elements. These can be phrases, clauses (especially non-defining relative clauses), appositives, and the like. Depending on the importance of the parenthetical element, the pair of commas that separate them can be replaced either by a pair of parentheses or by a pair of parenthetical dashes. The unimportant or lesser important details find shelter within a pair of parentheses; however, if the phrase needs to be emphasized, a pair of dashes are needed.
This choice can sometimes be obvious: I can immediately think of manufacturer details in the Methods section of scientific articles, which take parentheses. Sometimes it may not: At the beginning of this paragraph, I initially tried to enclose the phrase “especially non-defining relative clauses” within dashes. However, I ended up with parentheses as the second dash would clash with the separator comma; the dash being stronger would swallow the comma but would be inadequate to express the end of the list item. So, I decided the phrase can go within the parentheses, perhaps with some loss of emphasis.
Also noteworthy is the fact that the parentheses or dashes cannot replace commas in all of these cases. Think of a non-defining relative clause: Rarely can dashes replace them. Parentheses? Possible.
Where else commas are more frequent? Yeah, they appear before the coordinating conjunction connecting two independent clauses. Can something else replace commas here? You said it right; the semicolons can, of course also removing the conjunction. You already know the subtle difference between the two choices. This post has examples of semicolon use when connecting two independent clauses.
Okay, have you identified them? Can we move on? Commas sometimes are used to introduce other elements, especially display quotes and mathematical equations. Of course, as introductory commas, they are also used to introduce clauses. They are used to introduce inline quotes and direct speech. Many of these functions can well be played by colons. Colons are expert in introducing others. They are preferred over commas to introduce display items (lists, quotations and equations) – colon is the undisputed king here.
There is another place where commas cannot be used but only colons can be: when an independent clause is introduced to paraphrase or to add further meaning to an earlier clause. Sorry, Commander. Please step out.
So, in many instances, commas can be replaced to enhance clarity and readability, with semicolons, colons, parentheses, and dashes being the other choice.
Are commas indisputable somewhere?
They are. No other punctuation can replace commas after introductory phrases. You have some trailing thought to add after; can you think of anything other than commas? Nay. Perhaps a dash, but that sits there pretty artificially, doesn’t it?
Do you agree with me that commas are the commander of the punctuation weaponry?