Grammar lesson: more uses of commas

MORE USES OF COMMAS

NON-ESSENTIAL ELEMENTS

Sometimes parentheses are used to enclose information added to sentences that are extra information and not vital to the sentence making grammatical sense.

The year she was born (1964), her mother was living in Japan.

Commas can be used the same way.

The math teacher, Mrs. Garza, bought a Toyota.

The subject of the sentence is the math teacher, so saying the subject’s name is like repeating the same thing twice; it is the same person mentioned twice.

For this reason, it is considered grammatically non-essential, EVEN THOUGH it adds a piece of information about the subject that the reader might not know. That is why it is enclosed in commas.

This exact same principle applies if you switch the sentence to this:

Mrs. Garza, the math teacher, bought a Toyota.

It may seem silly to call extra information non-essential, but grammatically, it technically is, so that is why commas must go around the second iteration of something that is “named twice” so to speak. (The fancy grammatical term for this is an appositive, in case anyone is curious.)

THE “IF/THEN” PATTERN

In an “if/then” sentence, there must be a comma separating the IF part of the sentence from the THEN part.

If it rains, then the game will be cancelled.

This is true even if the word THEN is not explicitly stated.

If it rains, the game will be cancelled.

THE “NOT ONLY/BUT ALSO” PATTERN

In an “not only/but also” sentence, there must be a comma separating the NOT ONLY part of the sentence from the BUT ALSO part.

Not only did they win one game, but they also won the championship.

This is true even if one of the words in the pattern is not explicitly stated.

Not only did they win one game, they also won the championship.

Not only did they win one game, but they won the championship.

Not only did they win one game, they won the championship.

COMMA WITH LISTS OF ITEMS OR ADJECTIVES

Commas separate items in a list.

He bought rice, apples, beans, milk, tea, butter, and eggs.

This is true even when the items in the list are adjectives.

The kitten was tiny, cute, playful, fluffy, and hungry.

What happens when the items in the list are things that already have commas in them?

People at the meeting:

1. Jane, the art teacher
2. Al, the history teacher
3. Bibi, the French teacher
4. Kate, the math teacher

Or

Cities they visited:

1. Austin, Texas
2. Pueblo, Colorado
3. Trenton, New Jersey
4. Santa Fe, New Mexico

In those cases, the items are separated by semicolons.

The people at the meeting were Jane, the art teacher; Al, the history teacher; Bibi, the French teacher; and Kate, the math teacher.

The cities they visited were Austin, Texas; Pueblo, Colorado; Trenton, New Jersey; and Santa Fe, New Mexico.

THE OXFORD COMMA

Here is a video about this issue. Note that the APA prefers the use of it.

BONUS: The Oxford comma | Punctuation | Grammar | Khan Academy