I apologize in advance if my passion for the semicolon colors the language of this packet. The semicolon is one of the forms of punctuation that is easy to feel strongly about.
One of the reasons why the semicolon sparks such intense feelings among its devoted users is because it has the unique power of binding sentences together, and this alone makes the semicolon unique among the other forms of punctuation, whose functions (of no fault of their own) tend to separate and create distinctions. In contrast, the semicolon functions very much like connective tissue or glue. If there are similar ideas within two sentences, the semicolon quietly magnetizes them.
Unfortunately, the adhesive powers of the semicolon are widely misunderstood, and because they are misunderstood, the semicolon (of no fault of its own) also tends to be underused.
Its combined underuse and lack of appreciation surrounds the semicolon with an orb of mystery. Superficially, you might say that the “level” of pause it gives a sentence lies somewhere between the period and the comma; on a deeper note, you might notice that the semicolon exists somewhere in the twilight of the punctuation spectrum, binding ideas that need some agent to bring them together like positive ions bind with soil clay particles.
Because of these and other reasons, the semicolon deserves to be used appropriately, artfully, and often.
Source: Neil Cunningham
Semicolon rule #1: A semicolon can replace a period to separate two (or more) sentences that share similar idea that can be extended, qualified, or further explained with a second sentence. A semicolon signals to your reader that there is a relationship between two independently complete sentences that you want to emphasize equally.
Examples:
Beyond those hills is Green Mountain; no one has ever made the journey to the top and lived to tell.
There is an ancient volcano at the top of Green Mountain; the Monkey King lives inside a simple grass hut deep inside the mouth of the volcano.
The Monkey King has lived at Green Mountain ever since Sarah can remember; her mother says the Monkey King decided to leave the world because no one was paying attention to details like using the semicolon correctly.
Semicolon rule #2: Like the first rule, you can use a semicolon as “connective tissue” between two sentences; however, as you interrupt the flow of a sentence with a semicolon, you can pick up the second sentence with an introductory word (i.e., a conjunctive adverb) such as however, therefore, or an introductory phrase such as that is. Due to the natural pause that tends to follow an introductory word, it is preferred that a comma follows the introductory word.
Examples:
The Monkey King can leave the volcano anytime he wishes; however, he prefers to stay inside the volcano because the carelessness and thoughtlessness of the world makes him sad and angry.
If you ever go to visit the Monkey King, you should bring something that will show him that the world can also be thoughtful and caring; for example, you might consider baking a cake in the shape of a semicolon and then decorate it with black sugar frosting.
Semicolon rule #3: Use a semicolon to separate items in a list that contain commas within the list.
Examples:
The magic gathering has drawn wizards from London, England; Tokyo, Japan; Athens, Greece; and Juneau, Alaska.
Some of the problems with Sharna is that she is always late for events, meetings, and practices; she never says thank you when he receives a gift, free tokens, or a compliment; and she doesn’t seem to have a sense of when she is invading your personal space.
Semicolon rule #4: When one or more commas appears in the first sentence, you can use a semicolon between the two sentences that are joined by a conjunction.
Examples:
I know we are stuck, and space is tight, but you are invading my space; and I simply wish you would go and sit on the other side of the elevator.
If it can, the spaceship will lift out of the swamp; and if it can’t, there is no telling what the alien inhabitants will do to us.