Read up on where else to use that crucial comma in Part 2 of my rehash of the comma lesson.
That Crucial Comma – Part 2
Do not use commas to set off essential elements of the sentence, such as clauses beginning with that (relative clauses)
That clauses after nouns are always essential. That clauses following a verb expressing mental action are always essential.
Example: The dog that attacked me scared me.
Use a pair of commas in the middle of a sentence to set off appositives; nouns or noun phrases (starting with who, that, which) that explain the noun next to it in other words but are not essential to the meaning of the sentence
Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.
Example: I saw a finch, a kind of bird.
A kind of bird is the appositive, which gives more information about a finch.
Incorrect: Ben who is my brother called me.
Correct: Ben, who is my brother, called me.
Following are two instances of the need for an appositive comma with one or more nouns.
Incorrect: The three shopping items, a bottle of wine, a French bread stick, and some French cheese were in my bag.
Correct: The three shopping items, a bottle of wine, a French bread stick, and some French cheese, were in my bag.
If the appositive occurs in the middle of the sentence, like in the above sentences and in this one, both sides of the appositive need a comma. The closing comma is called an appositive comma. Many writers forget to add this important comma.
Example: Frances, who has a limp, was in a car accident.
If we already know which particular Frances is meant, the description is not essential and hence between commas.
Example: The boy who has a limp was in a car accident.
We do not know which boy is meant without further description; therefore, no commas are used.
This leads to a persistent problem. Look at the following sentence:
Example: My sister Jane is here.
Now, see how adding two commas changes that sentence’s meaning:
Example: My sister, Jane, is here.
Careful writers and readers understand that the first sentence means I have more than one sister. The commas in the second sentence mean that Jane is my only sister.
Why? In the first sentence, Jane is essential information: it identifies which of my two (or more) sisters I’m speaking of. Hence no commas enclose Jane.
In the second sentence, Jane is nonessential information—whom else but Jane could I mean?—hence the commas.
Comma misuse is not to be taken lightly. It can lead to lies like this:
Example: Jacky Dahlhaus’s book, Living Like A Vampire, is a delight.
Because of the commas, that sentence states that I wrote only one book. But I wrote at least three novels.
If something or someone is sufficiently identified, the description that follows, the appositive, is considered nonessential and should be surrounded by commas.
Incorrect: My best friend Joe arrived.
Correct: My best friend, Joe, arrived.
Use commas to separate three or more words, phrases, or clauses written in a series
Example: I saw a bird, a worm, and a fallen tree when I went walking.
Note: When the last comma in a series comes before and or or, it is known as the Oxford comma. It is generally used in the US, but not so in the UK and Australia.
Use commas to separate two or more coordinate adjectives that describe the same noun
Be sure never to add an extra comma between the final adjective and the noun itself or to use commas with non-coordinate adjectives (adjectives that can’t be separated by ‘and’).
Example: I saw a big, mean dog when I went walking.
Example: I saw two big dogs.
Only coordinate adjectives require a comma between them. Two adjectives are coordinate if you can answer yes to both of these questions:
1. Does the sentence still make sense if you reverse the order of the words?
2. Does the sentence still make sense if you insert ‘and’ between the words?
Since ‘I saw a mean, big dog’ and ‘I saw a big and mean dog’ both sound fine, you need the comma.
But, ‘I saw two and big dogs’ or ‘I saw big, two dogs’ don’t make sense. ‘Two’ and ‘big’ are non-coordinating adjectives, and therefore no commas are used.
Example: I eat the salty chicken soup.
Salty describes chicken soup as a whole phrase. This often occurs with adjunct nouns; a phrase where a noun acts as an adjective describing another noun — like ‘dance club’ or ‘summer sun.’
That’s it for today.