GRAMMAR | Commas - Run-Ons (Comma Splices) - Quotation Marks
Commas
Commas serve MANY different purposes in written English, and different rules govern these different purposes. Sometimes the choice of whether to use a comma is a matter of style, and in other situations the use of the comma is mandatory. Being comfortable and confident in your use of commas is essential to writing well in English!
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Here is an overview of some of the most important uses of commas in English:
1. Serial Comma: Commas for a Series of Things
1.1 Series of three or more items. Commas can be used to coordinate a series of three or more things. These things must be parallel: three words, three phrases, or even three clauses. The word "and" or the word "or" usually marks the last item in the series, but not always. Most people do not have much trouble with this type of comma usage.
- A fish should swim three times: in water, in sauce, and in wine.
three items at the end of the sentence: in water - in sauce - in wine
- Eat well, drink little, and sleep sound: in these three good health abound.
three items at the beginning of the sentence: eat well - drink little - sleep sound
- If it walks like a duck, quacks like a duck, and looks like a duck, it must be a duck.
three items in the middle of the sentence: walks like a duck - quacks like a duck - looks like a duck
1.2 Serial Comma Before "And." Some style guides say you should include a comma before the "and," while other style guides say you can leave out the comma before "and" - either way is fine with me!
- Comma before "and" is okay: Eat, drink, and be merry.
- No comma before "and" is also okay: Eat, drink and be merry.
2. Coordinating Commas: Comma Pairs and Single Commas
When a sentence has multiple parts, commas are often used to mark off those parts so that they are easy to recognize. Sometimes a PAIR of commas is required, and sometimes you can use a SINGLE comma.
2.1. Comma PAIRS INSIDE a Sentence. When a word, phrase or clause is being marked off INSIDE the sentence, the commas are used in a pair, much like the way parentheses are used as a pair:
- A houseguest, like a fish, stinks on the third day.
(pair of commas is used in middle of sentence)
- A gift, though small, is welcome.
(pair of commas is used in middle of sentence)
- Ink, if not used, will dry up.
(pair of commas is used in middle of sentence)
- An ox with long horns, even if he does not butt, will be accused of butting.
(pair of commas is used in middle of sentence)
2.2. SINGLE Commas at the BEGINNING or END of a Sentence. When a word, phrase or clause that would normally take a pair of commas appears at the beginning or end of a sentence, you need only one comma.
- When in Rome, do as the Romans do.
(the extra clause is at the beginning of the sentence, so only one comma is needed)
- Unless you enter the tiger's den, you cannot take the cubs.
(the extra clause is at the beginning of the sentence)
- The tongue is not steel, yet it cuts.
(the extra clause is at the end of the sentence, so only come comma is needed)
3. The Main Sentence and Extra Parts
A good way to think about comma usage is to find the main part of the sentence (the main subject and verb), and then see how extra phrases and clauses are added to that main sentence. There are many kinds of "extra parts" that can be added to the main sentence.
3.1. Prepositional, Adverbial and Adjectival Phrases
You will often find a comma used to set off these phrases at the beginning of a sentence, and sometimes in the middle of the sentence, as you can see in the following examples. (When such phrases are part of the predicate, coming at the end of the sentence, they are rarely set off with a comma.)
- In the dark, all cats are black.
- Feather by feather, the goose is plucked.
- Thinking about where you're going, you've forgotten where you came from.
- This,too, shall pass.
- The people, united, will never be defeated.
- An eel, held by the tail, is not yet caught.
3.2. Temporal Clauses and Phrases (When, Before, After, Until, etc.).
You can find temporal clauses most commonly at the beginning of a sentence or in the middle.
- When in Rome, do as the Romans do.
- Before you beat a dog, find out who its master is.
- Troubles, when sleeping, are not to be awakened.
3.3. Hypothetical Clauses and Phrases (If, Unless, Whether, etc.).
You can find temporal clauses most commonly at the beginning of a sentence or in the middle, and sometimes at the end of the sentence, too.
- If the dog's prayers were answered, bones would rain from the skies.
- Ink, if not used, will dry up.
- A fool, if he holds his tongue, passes for wise.
- God will be present, whether asked or not.
3.4. Causal Clauses and Phrases (Because, For).
Causal clauses and phrases are far more commonly found at the end of a sentence than at the beginning or in the middle.
- Look before you leap, for snakes in the grass may creep.
- Be careful what you ask for, because you just might get it.
- Agree amongst yourselves, because lawyers are expensive.
3.5. Result and Purpose Clauses and Phrases (So, Infinitives)
You will commonly find result and purpose clauses at the beginning, middle or end of a sentence.
- To know the road ahead, ask those coming back.
- Fish, to taste good, must swim three times: in water, in butter, and in wine.
- We're fools whether we dance or not, so we might as well dance.
- Be always a little afraid, so that you never have to be very afraid.
3.6. Concessive Clause and Phrases (Though, Although, Even If, However...)
You will commonly find concessive clauses at the beginning, middle or end of a sentence.
- No matter how full the river, it still wants to grow.
- However high a bird may soar, it seeks its food on the earth.
- A gift, though small, is welcome.
- There is no dog, be he ever so wicked, but wags his tail.
- Though the bird's in the net, it may get away yet.
- No man loves his fetters, even if they are made of gold.
3.7. Adversative Clauses and Phrases (But, Not, Nor, While).
Adversative clauses and phrases are almost always found at the end of the sentence, although you may sometimes find them in the middle of a sentence.
- A new broom sweeps clean, but an old broom knows the corners.
- It's easy to know people's faces, not their hearts.
- Little sticks kindle a fire, while great ones choke it.
- Look for the good, not the evil, in what others do.
3.8. Alternative Clauses and Phrases (Or, Else).
Alternative clauses and phrases are almost always found at the end of the sentence.
- Tell it well, or say nothing.
- A rich man is either a rogue, or a rogue's heir.
- Govern your passions, or they will govern you.
- Poverty does not destroy virtue, nor does wealth bestow it.
3.9. Expansive Clauses and Phrases (And).
Expansive clauses and phrases are almost always found at the end of the sentence. The use of a comma for these clauses and phrases is often optional. Read the sentence out loud and see how much you pause. If you can detect a meaningful pause, then use a comma.
- Many lose when they win, and others win when they lose.
- Catch the bear first, and then sell its skin.
- Genius is one percent inspiration, and ninety-nine percent perspiration.
3.10. Vocatives and Interjections
A "vocative" is when the speaker of the sentence is calling out to someone, addressing that person directly by name. This vocative address is not part of the grammar of the sentence, so it is set off with commas. The same is true for interjections. Because interjections are not part of the actual grammar of the sentence, they are set off with commas.
- Physician, heal thyself!
(the word "physician" is a vocative, so it is set off with a comma)
- When in Rome, my friend, do as the Romans do.
(the phrase "my friend" is a vocative)
- Beware of Greeks bearing gifts, O Trojans!
(the phrase "O Trojans" is a vocative)
- Well, that's the way the cookie crumbles.
(the word "well" is an interjection, so it is set off with a comma)
- Promise to stop and smell the roses, okay?
(the word "okay" is an interjection)
4. Relative Clauses (that, which, who, whom, what, etc.).
4.1. Non-essential information. When a relative clause is conveying non-essential information, something that feels truly "extra" to the sentence, it is set off with commas.
4.2. Essential information. When a relative clause is conveying essential information, then the opening comma is usually omitted. The closing comma may or may not be included. Read the sentence out loud and see if you pause at the end of the relative clause. If you pause at the end of the relative clause, that is a good indication that you should include a closing comma.
- He who doubts nothing, knows nothing.
(the relative clause is essential to the meaning, and is closed off with a comma)
- He who fights and runs away, lives to fight another day.
(the relative clause is essential to the meaning, and is closed off with a comma)
- Whom the gods would destroy, they first make mad.
(note that the antecedent of this essential relative clause has been suppressed)
- The finest and noblest ground on which people can live is truth.
(the relative clause is essential to the meaning, and it is not separated from the rest of the sentence by any commas at all)
5. Sentences with Two Equal Parts
5.1 Sentences in Two Parts. Sometimes instead of having a main part and extra parts, a sentence is composed of two equal parts. When a sentence is made up of two equally balanced halves, a comma is used to coordinate the two halves.
- As you sow, so shall you reap.
- The higher they fly, the harder they fall.
- The more things change, the more they stay the same.
5.2. BEWARE OF COMMA SPLICES. The two halves of the sentence cannot be sentences of their own. If you have two sentences that are connected with a comma, that is an example of a comma splice, which is the most common type of run-on sentence. For more information, see this page about Run-On Sentences.
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