A lot of punctuation and grammar issues in English tend to be subject to complaint that “even the exceptions have exceptions,” which makes it all seem hopelessly chaotic.  It’s useful, when that sort of overwhelming entropy threatens to overtake you, to find a small part of the language that allows you to see how things work on a small scale.

One of those parts is a concept called an “appositive.”  It’s a useful one, because it can open up an understanding of how a number of otherwise inscrutable punctuation marks really are designed to function, from the seemingly random comma, to the baffling periods of ellipsis. 

An appositive is a word or phrase within a sentence that restates a noun in other terms.  It’s kind of like a short definition or clarification of the main subject idea.  Here’s an example: “Tom Evans, a local Welshman, grew leeks.”  In the example “a local Welshman” is another way to understand the main subject “Tom Evans.”  The phrase could be a as short as one word (“John Evans, president, grew leeks”), or much longer (“Tom  Evans, a man who once found himself trapped alone in a flooded house with a rabid mountain lion and a jar of pickled beets to defend himself with, grew leeks”).  The length doesn’t matter, as the punctuation rules are the same.

An appositive must be surrounded by punctuation.  If it comes in the middle of the sentence, the punctuation variation is substantial.  If it comes at the end of a sentence, the mysterious colon can be used.

Let’s start with the last part first: colons.  A colon is a punctuation mark that is designed to introduce appositives.  That is the primary function, regardless of how messy the sentence looks in the end.  Anything the follows after a colon is on some level a restatement of what was on the other side, as in: “The weather was the worst kind: a hurricane.”  It can only do so at the end of a sentence, because the whole phrase after the colon has to be an appositive, and that’s the only logical way it can work.  

In the middle of a sentence, an appositive can be surrounded on both sides by a range of punctuation types, each with its own effect.

A comma is the most neutral way to set off an appositive.  To return to our example: “Tom Evans, a carnivore, grew leeks.”  The information about Evans’ meat-eating preferences is simply stated as part of the sentence.  No extra emphasis or tone is communicated through the use of the punctuation, which is why you most frequently see appositives use them.

If we re-arrange the sentence to allow for a colon (remember, it has to end as a complete appositive), we’d have something like: “The man who grew the leeks was Tom Evans: a carnivore.”  In this case, there seems to be some implied heightened attention to the fact that the appositive detail might be in contrast with the action of the sentence.  In other words, the sentence reads as though Evans’ carnivorosity makes it surprising that he grew the leeks.

A colon states that there is a direct value connection between the appositive and the initial subject—they are the same in different words.  A more modern punctuation mark makes a related, but weaker case.  Two hyphens (-) together create a dash (--).  A dash indicates that the things it connects are strongly related, but not identical.  Some other time we’ll look at how this explains why dashes are so prevalent in our country’s founding documents, as well as the writings of suffragists, abolitionists, and revolutionaries.  The dash was seen at the time as a radical grammatical escape from the tyranny of the colon.  I know.  

In any case, “Tom Evans—a carnivore--grew  leeks” is a sentence that is not neutral.  It has some of the same tone implications as is created by the colon at the end of the sentence.  But because it’s a more flexible punctuation mark (a liberty dash!), it can be used in the middle of the sentence to call attention to the appositive.

The opposite tone (sublimation as opposed to emphasis) will result from the use of our friend the parenthesis.  Parenthesis are used to present appositive ideas that are primarily explanatory, and not designed to be of greater or equal importance to the main subject.  They are basically ways of providing a quick definition by synonym for a reader.  Visually, they also create an easy way for readers to find a definition by scanning the text.  This is why acronyms are often encased in parenthesis: “Tom Evans grew leeks for WEU (Welsh Eaters Unite) last year.”  The parenthesis are unobtrusive and information-forward.

There are even more ways to punctuate appositives, but the last main method is with the use of the three dots…officially termed the “periods of ellipsis.”  This is something of a specialized punctuation mark.  In writing, it indicates that something has been left out of the text.  This can be used to create a number of tones, from suspense to sarcasm.  “Tom Evans…a carnivore…grew the leeks.”  The effect in many case is similar to “there’s so much I could say here, but I’m not going to!”  When used inside quotation marks, it means that the original text being quoted has been edited to remove something.

Word of the Week: Biweekly.  Be on the lookout for this absolute hand grenade of a word.  Because of its derivation and usage over time, it means “once every other week” AS WELL AS “twice a week.”  Most usage dictionaries will tell you to avoid it for the obvious potential to create chaos.  Imagine a payroll department who crossed their lines on which one it meant.  Imagine a bedraggled committee chair trying to get people to attend meetings scheduled using the term.  Just avoid it like the plague.  The word “semiweekly” is sometimes used in place of it, since that one literally means “twice a week.”  But really, just use a number or dates when there is any potential for pandemonium.