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Punctuation Guide


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Punctuation is the use of symbols (punctuation marks) to add meaning or clarify written language. Punctuation marks don't correspond to sounds, but may indicate where to leave pauses when reading text aloud.

Commonly-used punctuation marks

Full stop [.]

The full stop or period, also called a full point, is the punctuation mark commonly placed at the end of sentences. A period consists of a small dot placed at the end of a line of text.

The period is also used after abbreviations, such as Mr., Dr., Mrs., Ms. If the abbreviation is ending a sentence the second period is not needed unless the sentence ends with a question or exclamation mark.

Comma [,]

The comma is used to mark off separate elements in a sentence: introductory clauses, words in a series, parenthetical phrases, or interjections. Commas are also used to separate items in lists, and to present large numbers in a more readable form.

These formal uses frequently also indicate a pause in speech. Writers often use optional commas for stylistic reasons, to indicate such a pause where none may be required, grammatically.

The comma is also used to separate two independent clauses (a group of words that can function as a sentence) that are joined by a co-ordinating conjunction ("and" & "but" when they are used to connect), eg:

"I passed the test, but he failed." -- "I passed the test" and "He failed" can function as separate sentences.

An important, often misunderstood use of the comma is for thought interruptions. Information that is unnecessary to the meaning of the sentence must be set off and ended by a comma. If the information is necessary, no commas should be used.

"I cut down all the trees, which were over six feet tall." -- In this sentence, all of the trees were over six feet tall and were cut down. Therefore, this information is unessential and "which" is used.

"I cut down all the trees that were over six feet tall." -- In this sentence, only those trees over six feet tall were cut down. Therefore, this information is essential and "that" is used.

Semicolon [;]

In English, the semicolon has two main uses:

  1. It binds two sentences more closely than they would be if separated by a full stop or period. It often replaces a conjunction such as and or but. A writer might consider this appropriate where they are trying to indicate a close relationship between two sentences, or a 'run-on' in meaning from one to the next; they don't wish the connection to be broken by the abrupt use of a full-stop.
  2. It is used as a stronger division than a comma, to make meaning clear in a sentence where commas are already being used for other purposes. A common example of this use is to separate the items of a list when some of the items themselves contain commas.

There are several rules that govern semicolon placement:

  1. Use a semicolon between closely related independent clauses not joined by a coordinating conjunction: "I went to the store; they were closed."
  2. Use a semicolon between independent clauses linked with a transitional phrase or conjunctive adverb: "I like to ride horses; however, they don't like to ride me."
  3. Use a semicolon between items in a series containing internal punctuation: "There are several Waffle Houses in Atlanta, Georgia; Greenville, South Carolina; Pensacola, Florida; and Mobile, Alabama."

Some experts will allow for a semicolon to separate independent clauses that are joined by coordinating conjunctions when the clauses have internal commas that might lead to misreading:

"After the game, I won a red beanie baby, four edible ingots, and a certificate of excellence; but when the storm came, I lost it all in a torrent of sleet, snow, and profanity."

Semicolons are always placed after closing quotation marks and are never followed by an uppercase letter, unless that letter begins a proper noun.

Colon [:]

Colons are commonly used to introduce lists, or to connect a broad idea with a specific example: two related sentences can be separated by colons instead of full stops or semicolons. Colons may also be used to introduce a direct quote, or to draw attention to an appositive (a noun phrase that generally follows, but occasionally precedes, another noun phrase and renames or describes it). In any of these cases, a colon can only be used if the clause preceding the colon is independent.

In American English colons are also used after the salutation in a formal letter, Dear John:

When closing quotation marks and colons are adjacent, the colons always follow. Capitalization following colons is optional.

Apostrophe [']

An apostrophe is commonly used to indicate omitted characters as in:

  • abbreviations, as gov't for government, or '70s for 1970s.
  • contractions, such as can't from cannot and it's from it is or it has.

An apostrophe is used with an added s to indicate possession, as in Oliver's army, Elizabeth's crown. If a name already ends with an s the extra s is sometimes dropped: Jesus' parables.

An apostrophe is used by some writers to form a plural for abbreviations and symbols where adding just s rather than ’s would be ambiguous, such as mind your p's and q's. It is not necessary where there is no ambiguity, so CDs not CD's, videos not video's, 1960s not 1960's, 90s or '90s not '90's.

Things to watch

  • The apostrophe in it's marks a contraction of it is or it has. The possessive its has no apostrophe, eg the dog hurt its paw.
  • Who's means who is or who has. The possessive of who is whose. The person whose responsibility it is is the member who's oldest.
  • You're means you are. This is different from the possessive your. Your nuts implies the nuts belong to you. You're nuts would mean You are nuts.
  • When the noun is plural and already ends in s, no extra s is added in the possessive, so pens' lids (where there is more than one pen) rather than pens's lids. If the plural noun doesn't end in s, then add s as usual: children's hats.

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This article is licensed under the GNU Free Documentation License. It uses material from the
Wikipedia articles:S "Punctuation", "Full stop", "Comma (punctuation)", "Semicolon",
"Colon (punctuation)", "Apostrophe (mark)", "Quotation mark", "Question mark",
"Exclamation mark", "Dash", "Hyphen", "Slash (punctuation)", "Bracket", "Ellipsis".