In my last MM, I talked about using semicolons as “softer periods” to join two sentences into one. That’s the main use of this mark of punctuation, but there’s another instance in which you’ll see it: the complex list. This use of the semicolon is unrelated to its main function.

Here’s a simple list:

Fred went to the store and bought milk, eggs, and cat food.

It’s pretty easy to figure out the items in this list, as they’re separated from one another with commas:

A = “milk”
B = “eggs”
C = “cat food”

But what if A, B, and C are longer and more complex? What if you get lists within your lists?

Joe Doe is survived by his wife, Nancy Smith, his sister Samantha, his three sons, Paul, Edward, and James, his daughter, Jane, six grandchildren, Sally, Janine, Robert, John, Peter, and Frank, and one great-grandchild.

A complex list is a list in which at least one individual item contains a comma. For instance, in the above sentence, C = “his three sons, Paul, Edward, and James.” The commas that separate C from B and D blend together with the commas inside C. That makes the above sentence pretty hard on a reader: she can’t tell immediately where C begins and ends. Instead, she has to read slowly, grouping the names into categories as she goes. The point of punctuation is to make things easier for your reader. In the above sentence, punctuation is not going its job.

Semicolons clarify complex lists by replacing the commas between items. Here’s what the above sentence looks like when punctuated correctly:

Joe Doe is survived by his wife, Nancy Smith; his sister Samantha; his three sons, Paul, Edward, and James; this daughter, Jane; six grandchildren, Sally, Janine, Robert, John, Peter, and Frank; and one great-grandchild.

Having even one item with one internal comma is enough to trigger complex-list punctuation, but if you don’t have at least three items, you don’t have a list:

Fred went to the store and bought milk and a bunch of pet supplies, including cat food and bird seed.

“Milk” and “pet supplies” aren’t a list, and “cat food” and “bird seed” aren’t a list, either. Only when you get three or more items to you have to start thinking about list-punctuation issues.