Commas: Correct Usage & Basic Rules

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  • 0:06 Willy-Nilly Comma Usage
  • 0:27 Separating Elements in…
  • 2:04 Separating Adjectives…
  • 2:50 After an Introduction
  • 4:03 Inside Quotation Marks
  • 4:52 Lesson Summary
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Lesson Transcript
Instructor: Christopher Curley
Think that you know commas? You may be surprised. Even the most experienced writers have problems remembering all the rules. Learn the basics of comma usage in this first of two lessons on the comma.

Correct Comma Usage

Do you get confused when trying to place a comma in a sentence? Are you befuddled when the commas you thought you'd placed correctly in your paper come back with red marks all over them, moved about seemingly willy-nilly? Unfortunately, the only way to defeat this scourge of grammatical correctness is to know your comma usage rules. So let's take a look at a few of the most common ways to use commas.

Separating Elements in a Series

The comma is used to signify a slight pause in a sentence. These pauses are more slight than a period, exclamation mark, question mark, or semicolon, but it is there nonetheless. The first, most basic way you're taught to use a comma is for separating elements in a series, as in, ''McBliver was able to build a rudimentary thermonuclear reactor with a cheese wedge, a half-empty Diet Coke, and some Uranium-235.''

As you can hear in my voice, I pause a bit before listing each item in the series. Otherwise I'd have to say, ''a cheese wedge a half-empty Diet Coke and some Uranium-235,'' and you'd have a hard time understanding what I was saying.

Some teachers will tell you that you have the option of whether or not you want to include the final comma in the series before the conjunction (in this case, it's the comma preceding ''and some Uranium-235''), and they're not wrong, but I'd advise that you leave it in. When you leave that comma in, it's called the Oxford comma or serial comma because it punctuates the last item in a series.

While both are grammatically correct, not including the last comma can lead to confusion. For instance, let's say we're not separating single items but several separate thoughts. ''To the left here, you'll see the lion cages, the piranha tank, the battleship and administrative offices.'' Without a comma before the final conjunction, it's not clear whether the battleship and administrative offices are separate things or if the battleship also contains the administrative offices. So when in doubt, leave the comma before the conjunction in. That way, more clearly, it would read, ''To the left here, you'll see the lion cages, the piranha tank, the battleship, and administrative offices.''

Separating Adjectives from Each Other

The other way that you may be familiar with using commas is to separate the adjectives that describe a noun. However, you may have also noticed that it's not always consistent. For instance, which of the following is correct? ''Tyrone had a strong, legendary appetite'' or ''Tyrone had a strong legendary appetite?''

The answer is the first option. Remember that if you can put 'and' between the adjectives that describe the noun and they still make sense, then there should be a comma in between them. Otherwise, leave it out.

Here's a counter-example: ''Matilda loves organic chicken eggs.'' In this case, there's no comma between the adjectives because they both have equal status in describing the noun 'eggs.' They're not organic AND chicken AND eggs but one complete thought: organic chicken eggs. Hence, no comma is necessary.

After an Introduction

Another time you'll use commas is when introducing any word or phrase that comes before the main clause in the sentence (that's the part of the sentence with at least one subject and one verb that's the most essential -- for more on this see the lesson on independent clauses).

''Yes, I will have that bacon sandwich. However, I can't eat it in front of that pig. It's like he knows!'' In this case, both 'yes' and 'however' are introductory words, so they need to have a comma after them. If the introductory word (not so introductory anymore, but stick with me) is at the very end of the sentence, then it has to have a comma preceding it. As in, ''I can't eat it in front of that pig, however.''

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