Why, oh why, do so many people not know how to use a comma? I am a pretty active reviewer on the GAN page, and rare is the article where I do not have to fix multiple instances of failure to use commas properly. To be honest, I'm a little perplexed by this, seeing as how it's really not that complicated. What follows is a guide on how to properly utilize commas in writing. This is not meant to be an exhaustive guide that covers every little obscure rule (of which there are several), just a basic tip sheet on the most common situations and errors in encyclopedic writing.
Comma use guide
Joining two thoughts
This is, by far, the most common error. When joining two thoughts into a single sentence by using a conjunction, a comma should be used only if both portions of the sentence can stand alone (and make sense) as complete sentences. Let's look at an example:
- "The Melida leader informed the Jedi that headquarters was a weapon-free zone, and that they would have to leave their lightsabers outside."
- Wrong. At first, it appears that the comma is correct since "They would have to leave their lightsabers outside." is a complete sentence, but let's look closer. There is another word—"that"—immediately after the conjunction ("and") that must be considered. After including the extra word, the second part of the sentence comes out as follows: "That they would have to leave their lightsabers outside." This makes no sense and cannot stand alone, as it relies on the first six words of the main sentence, and therefore no comma should be used.
- "The Melida leader informed the Jedi that headquarters was a weapon-free zone and that they would have to leave their lightsabers outside."
- Correct.
If a parenthetical expression that needs to be surrounded by commas (see below) immediately follows the conjunction, things are even more complicated. First determine whether each part of the sentence can stand alone. If they can, then the first comma should be placed before the conjunction, with no comma after it. If one or both parts cannot stand alone, then the parenthetical expression should be punctuated as normal, with the first comma after the conjunction. Example:
- "Each of the Azzameen children intercepted the saboteurs and incoming CloakShape fighters and, after the Azzameens' display of power, the End Run completed the transfer and exited the system."
- Wrong. Ignore the need for commas for the parenthetical expression for the moment and focus on whether each part of the sentence can stand alone. They can, so the first comma goes before the conjunction, since two complete sentences are being joined together.
- "Each of the Azzameen children intercepted the saboteurs and incoming CloakShape fighters, and after the Azzameens' display of power, the End Run completed the transfer and exited the system."
- Correct. No comma should be used immediately after the conjunction.
Another example:
- "Jinn had located a hologram recorded by Cerasi on the morning of her death, and upon arriving at the scene of the battle, played it from atop a nearby fountain."
- Wrong. This is the opposite of the previous example. In this case, "Upon arriving at the scene of the battle, played it from atop a nearby fountain." is not a complete sentence as there is no subject. Therefore, the first comma should be placed after the conjunction.
- "Jinn had located a hologram recorded by Cerasi on the morning of her death and, upon arriving at the scene of the battle, played it from atop a nearby fountain."
- Correct.
Parenthetical expressions
Another common error involves whether to surround parenthetical expressions and subordinate clauses with commas. You should do so only when removing the phrase from the sentence would not change the meaning of the sentence. Example:
- "Echo, and the remaining clone troopers, witness the destruction of the base."
- Wrong. The addition of the phrase "and the remaining clone troopers" changes the meaning of the sentence by specifying that multiple clones watched the destruction of the base, not just Echo. No commas should be used.
- "Echo and the remaining clone troopers witness the destruction of the base."
- Correct.
Another example:
- "The two tribes, collectively known as the Elders by the Young, initially had the upper hand with several starfighters."
- Correct. In this case, removing the nonessential clause "collectively known as the Elders by the Young" does not change the meaning of the sentence, which is that the two tribes had the upper hand. Therefore, the use of commas surrounding the phrase is correct.