The Semicolon: Parts 1, 2, and 3, by Zachary Koppelmann.
Semicolons are used in two basic ways:
To connect two closely related sentences and to separate items in a list or series.
Connecting Two Closely Related Sentences
Here is an example.
Cats have fur; they are soft.
These are two complete sentences that are related.
A semicolon can be used to connect them for greater emphasis.
Listen to the difference between "Cats have fur. They are soft." and
"Cats have fur; they are soft."
A semicolon creates a shorter pause,
which puts emphasis on the connection between the sentences.
In this usage of the semicolon, the semicolon can replace
a comma and coordinating conjunction.
"Cats have fur, and they are soft"
or "Baseball is boring, so I prefer hockey."
or "I am hungry, but I hate Brussels sprouts."
In all of these cases, the comma and conjunction can be replaced
by a semicolon to add emphasis.
The semicolon is a tool you can use to help guide your reader.
It is rarely required, and it should be used only sparingly
with closely related sentences.
You would not write, "Cats have fur; baseball is boring."
Separating Items in a List or Series
Here are two examples.
When we traveled over break, we stayed in a number of places:
Cheyenne, Wyoming; Denver, Colorado; Boise, Idaho; and Salt Lake City, Utah.
and
We traveled across a few states:
Indiana, Iowa, Nebraska, Kansas, Idaho, Wyoming, Utah, Colorado, and Missouri.
Both examples contain lists,
but one uses semicolons to separate each element in the list,
while the other uses commas.
Both examples are correct, but the elements within the lists are different.
In the first example, each element already has a comma.
"Cheyenne, Wyoming"
To avoid confusion, a semicolon is used to separate the elements.
Otherwise, the sentence would look like this:
When we traveled over break, we stayed in a number of places:
Cheyenne, Wyoming, Denver, Colorado, Boise, Idaho, Salt Lake City, and Utah.
Now it looks like Boise and Wyoming are equal places, not a city and a state.
This use of the semicolon is the only one that's required
and is only required in a list or series in which an element already has a comma.
It is important to note that you may see a semicolon
used to separate elements in a list in which the elements do not already have commas.
The elements are much longer phrases or complete sentences.
This is done to help the reader better understand the sentence,
and is technically correct.
However, it is very rare and should be avoided.
This covers the two basic rules for using semicolons,
but the rules are not always enough.
At times, it's important to see a semicolon used
and to hear their effects before being able to expertly use them.
Here is a series of examples meant to demonstrate more sophisticated uses of semicolons.
Project Steam Power is over budget and behind schedule; however, the design team has made some impressive discoveries.
versus
Project Steam Power is over budget and behind schedule. The design team has made some impressive discoveries.
Using a semicolon in this case creates emphasis and direction.
It allows you to direct the reader's attention.
This can be useful when you need to highlight one bit of information over another.
The project leader is not answering the phone; we need to take over.
versus
The project leader is not answering the phone. We need to take over.
Using a semicolon in this case answers the implied question,
"What do we do when the project leader does not answer the phone?"
It makes a closer connection between the reason and the action.
Sophisticated use of semicolons can add emphasis, direct the reader, and build specific connections between ideas.
While the semicolon can be a useful tool,
it is important not to overuse them.
Overuse can weaken their effect.
If you have any questions, please contact your TA.
This has been "The Semicolon: Parts 1, 2, and 3" by
Zachary Koppelmann, in cooperation with the Purdue Online Writing Lab and prepared for the Mechanical Engineering Writing Enhancement Program.