ABOUT COMMA PUNCTUATION
First of all, we should note that comma usage is not fixed across the English-speaking world. The Brits have differing views about commas – and punctuation in general – from their American cousins. And that’s only the start. What we can agree on is that commas are important to make meanings clear, as in the old textbook example: The boss, thought the clerk, was crazy. and The boss thought the clerk was crazy. Who exactly is crazy? It’s not hard to see that a misplaced comma or two can dramatically alter the meaning of your sentence.
And on the topic of sentences, a sentence is made up of a subject, a main verb and a complement (for those slightly grammatically challenged, don’t feel bad about it!) a complement is the additional word or words that adds meaning to the verb and tell us things like what, when, to whom, etc. For instance: She (subject) ate (main verb) onion rings (complement). Here, there is no need for commas.
All complete sentences end with a period. Beware of the comma-splice trap and run-on sentences (more on those another time). Each sentence must have a subject and a verb, but not necessarily a complement. I struggle is a complete idea and a complete sentence in itself, with only a subject + verb.
A sentence may have two or more complements to add further meaning to the sentence. You can recognize the complement if you ask “what, when, where, how...” She ate onion rings (compl. #1) at the restaurant (compl. #2). You can even pile on the complements: She ate onion rings (#1) with her fingers (compl. #3) at the restaurant (#2) the previous evening (compl. #4).
You’ll notice that above we have compl. #3 before compl.#2 but it still reads correctly and there’s still no need for comma. But other constructions do require commas, such as if we move the complements around and provide what is called parenthetical information: At the restaurant, the one on the corner of First and Main, the previous evening, she ate onion rings with her fingers. Commas are needed to separate the complements indicating place and time, particularly since they come before the subject-verb component.
Recap. You need commas to separate elements of a sentence that are closely related or dependant on the basic sentence and add meaning to it. Remember, the main sentence is always made up of a subject and a verb.
A comma is always needed to separate items on a list:
He packed shirts, socks, ties, underwear and a hat. The first item shirt comes directly after the verb and of course doesn’t need a comma in front but does after it, as as do all the subsequent listed items except the last, which is joined with and.
A comma is also needed to separate a series of actions: The skier missed the turn, lost his balance, fell sideways and came to rest against the safety net. Really, this is still a list.
A comma is needed when a person’s name or qualifier is introduced in a narrative: The baker’s daughter, Jenny, served the customers. or in dialogue: “Did you met Jenny, the baker’s daughter, when you went shopping?”
However. Place a comma after “however” unless it means “in whatever way.” Hence: However you look at it, the computer is here to stay. But The rainstorm struck in the late afternoon. However, everyone reached home safely.
But. In the sentence The restaurant is expensive but very good no comma is needed after but because what follows is directly related to the sentence. When two separate statements are in opposition to each other, a comma is needed: The introduction of wild boars was thought to be an improvement, but no one knew they would destroy the habitat.
And. The conjunction and is a linking word, therefore no comma is needed, unless it introduces a second sentence to add information or an interjection to the main sentence: She plays the violin badly, and what’s worse, she plays it at midnight. and For large trucks, air brakes are of vital importance, and they need to be serviced regularly.
ING. Despite being considered poor writing, participle phrases – ones that start with the -ing form of the verb – are often found in what is regarded as fine literature: Consider the sentence Opening the door, Fred walked away from the house. A comma is needed after the adverbial phrase Opening the door to separate it from the second action walked away. Think again before starting a sentence with this type of construction. The participle is not a finite form of the verb. In other words it has no time limitation. Grammatically it is an action with no ending and we have the logically impossible scenario of Fred opening that door all the while he’s walking away from the house! Participle constructions are so common in writing that many people don’t even notice them and don’t see the illogicality.
In dialogue, when a statement is made followed by a question, a comma is needed: You saw the accident, didn’t you? and You didn’t drink all the martinis, did you?
Also when there is an interjection. “Wait, you have forgotten your tickets” and No, I don’t want to go to the movies tonight.
And, of course, a comma is used to end a dialogue line if it is followed by an attribution (a tag), either at the end: “Take my car,” he said, or in the middle, as in: “Be careful,” he said, “there are many dangers.”
Recap. We use commas to make the meaning of written language clear. It’s worth stopping and taking a critical look at your sentence patterns. It won’t be long before you’ll know instinctively where to use a comma.