Answer: The difference between semicolons and colons
rykaine asks: What is the difference between a semicolon and a colon?
With examples from Stargate SG-1, Stargate Atlantis, and Torchwood.
Semicolons and colons are incredibly useful for the construction of complex and interesting sentences that can't be made with your usual stable of commas and periods. Unfortunately, semicolons and colons are often used inappropriately and confused for each other. In this answer I'm going to give an overview of what exactly semicolons and colons are used for, and how to tell when to use one over the other.
Semicolons
A semicolon is a punctuation mark that, when used in a statement, indicates a longer pause than a comma but a shorter pause than a period. There are a couple situations where the use of a semicolon is appropriate.
First, and what you'll most commonly come across, is the use of a semicolon to connect two independent clauses without having to use a coordinating conjunction (such as "and" or "but") and without having to split the two clauses into separate sentences. In this instance the semicolon is mostly a stylistic choice, which writers will use to connect two statements that are closely related.
Let's look at the following:
Daniel didn't want to hear Vala's excuses, and he wasn't in the mood to deal with her antics.
In that sentence, a comma and a conjunction ("and") are used to divide two independent clauses. That same line can be rewritten as two separate sentences:
Daniel didn't want to hear Vala's excuses. He wasn't in the mood to deal with her antics.
But the line can also be written with a semicolon as the divider:
Daniel didn't want to hear Vala's excuses; he wasn't in the mood to deal with her antics.
All of these examples are correct. Which one is preferred is completely up to the writer, their personal style, and which they feel sounds best in context.
So what would be incorrect?
Using a comma with no conjunction. This is called a comma splice and should be avoided:
Daniel didn't want to hear Vala's excuses, he wasn't in the mood to deal with her.
Using a semicolon with a coordinating conjunction. In this case a simple comma is sufficient:
Daniel didn't want to hear Vala's excuses; and he wasn't in the mood to deal with her.
What's important to keep in mind is that a semicolon can only be used like this to separate two independent clauses, which means both statements on either side of the semicolon must have a subject and a predicate. It is not correct to use a semicolon to connect two dependent clauses, or to connect an independent clause with a dependent clause, such as in the following example:
O'Neill rolled his eyes; sighing.
The statement after the semicolon is a dependent clause, so the correct punctuation mark would be a comma.
Another common use of the semicolon is as a "supercomma," where a semicolon takes the place of a serial comma where using serial commas would be confusing (see this entry for more information on serial commas).
Take the following example:
The three existing Torchwood branches are in London, England, Cardiff, Wales, and Glasgow, Scotland.
That sentence is confusing because the commas are being used as serial commas and as separators in place names, and there's no easy way to distinguish them. Enter the semicolon, making the revised sentence looks like this:
The three existing Torchwood branches are in London, England; Cardiff, Wales; and Glasgow, Scotland.
The semicolon clarifies things. Also, take a look at that last semicolon in the previous example. It's followed by a conjunction ("and"). I just said that was incorrect, didn't I? Actually, that particular construction is the only time in which a semicolon + a coordinating conjunction is correct.
There are other uses for the semicolon, but these are the basic ones. The Wikipedia entry on semicolons is a good place to start if you want more particulars.
Colons
A colon is usually used between a statement and another statement that follows directly on from the previous statement. In other words, there is an independent clause, a colon, and then an explanation, clarification, or enumeration of the preceding independent clause.
A neat example I found while researching this topic is to think about the colon as a gate that opens to more information about the statement you just read.
So what does this mean in practical terms? Colons can be used in the following constructions:
1. A statement showing a consequence or effect.
Rodney McKay knew there could be only one reason why his experiment wasn't working: Zelenka must have touched his stuff.
2. A statement containing elements of a set.
Sheppard knew the Wraith thought Atlantis would never be able to rescue him, but they weren't taking into account three things: McKay, Teyla, and Ronon.
Like with semicolons, the first statement of the construction must be an independent clause. But unlike semicolons, the part of the sentence after the punctuation mark does not have to be another independent clause. In my examples above, the first is two independent clauses connected with a colon. The second example, however, does not contain two independent clauses but is still correct.
A colon is also used for miscellaneous other things outside of sentence construction, such as after the salutation on a business letter (Dear Sir:), as a separation in a written time of day (12:45), as a separation of title and subtitle (Stargate SG-1: The Ark of Truth), and several other cases. Again, the Wikipedia article on colons is a good place to see an enumeration of all the various uses of the colon.
With examples from Stargate SG-1, Stargate Atlantis, and Torchwood.
Semicolons and colons are incredibly useful for the construction of complex and interesting sentences that can't be made with your usual stable of commas and periods. Unfortunately, semicolons and colons are often used inappropriately and confused for each other. In this answer I'm going to give an overview of what exactly semicolons and colons are used for, and how to tell when to use one over the other.
Semicolons
A semicolon is a punctuation mark that, when used in a statement, indicates a longer pause than a comma but a shorter pause than a period. There are a couple situations where the use of a semicolon is appropriate.
First, and what you'll most commonly come across, is the use of a semicolon to connect two independent clauses without having to use a coordinating conjunction (such as "and" or "but") and without having to split the two clauses into separate sentences. In this instance the semicolon is mostly a stylistic choice, which writers will use to connect two statements that are closely related.
Let's look at the following:
Daniel didn't want to hear Vala's excuses, and he wasn't in the mood to deal with her antics.
In that sentence, a comma and a conjunction ("and") are used to divide two independent clauses. That same line can be rewritten as two separate sentences:
Daniel didn't want to hear Vala's excuses. He wasn't in the mood to deal with her antics.
But the line can also be written with a semicolon as the divider:
Daniel didn't want to hear Vala's excuses; he wasn't in the mood to deal with her antics.
All of these examples are correct. Which one is preferred is completely up to the writer, their personal style, and which they feel sounds best in context.
So what would be incorrect?
Using a comma with no conjunction. This is called a comma splice and should be avoided:
Daniel didn't want to hear Vala's excuses, he wasn't in the mood to deal with her.
Using a semicolon with a coordinating conjunction. In this case a simple comma is sufficient:
Daniel didn't want to hear Vala's excuses; and he wasn't in the mood to deal with her.
What's important to keep in mind is that a semicolon can only be used like this to separate two independent clauses, which means both statements on either side of the semicolon must have a subject and a predicate. It is not correct to use a semicolon to connect two dependent clauses, or to connect an independent clause with a dependent clause, such as in the following example:
O'Neill rolled his eyes; sighing.
The statement after the semicolon is a dependent clause, so the correct punctuation mark would be a comma.
Another common use of the semicolon is as a "supercomma," where a semicolon takes the place of a serial comma where using serial commas would be confusing (see this entry for more information on serial commas).
Take the following example:
The three existing Torchwood branches are in London, England, Cardiff, Wales, and Glasgow, Scotland.
That sentence is confusing because the commas are being used as serial commas and as separators in place names, and there's no easy way to distinguish them. Enter the semicolon, making the revised sentence looks like this:
The three existing Torchwood branches are in London, England; Cardiff, Wales; and Glasgow, Scotland.
The semicolon clarifies things. Also, take a look at that last semicolon in the previous example. It's followed by a conjunction ("and"). I just said that was incorrect, didn't I? Actually, that particular construction is the only time in which a semicolon + a coordinating conjunction is correct.
There are other uses for the semicolon, but these are the basic ones. The Wikipedia entry on semicolons is a good place to start if you want more particulars.
Colons
A colon is usually used between a statement and another statement that follows directly on from the previous statement. In other words, there is an independent clause, a colon, and then an explanation, clarification, or enumeration of the preceding independent clause.
A neat example I found while researching this topic is to think about the colon as a gate that opens to more information about the statement you just read.
So what does this mean in practical terms? Colons can be used in the following constructions:
1. A statement showing a consequence or effect.
Rodney McKay knew there could be only one reason why his experiment wasn't working: Zelenka must have touched his stuff.
2. A statement containing elements of a set.
Sheppard knew the Wraith thought Atlantis would never be able to rescue him, but they weren't taking into account three things: McKay, Teyla, and Ronon.
Like with semicolons, the first statement of the construction must be an independent clause. But unlike semicolons, the part of the sentence after the punctuation mark does not have to be another independent clause. In my examples above, the first is two independent clauses connected with a colon. The second example, however, does not contain two independent clauses but is still correct.
A colon is also used for miscellaneous other things outside of sentence construction, such as after the salutation on a business letter (Dear Sir:), as a separation in a written time of day (12:45), as a separation of title and subtitle (Stargate SG-1: The Ark of Truth), and several other cases. Again, the Wikipedia article on colons is a good place to see an enumeration of all the various uses of the colon.