“Put a comma in whenever you take a breath.”

Almost everyone I know has heard that particular comma rule, or some variation of it, and that is unfortunate because the rule is unreliable at best and, at worst, simply wrong. But the rule does make sense in a historical context, and that may explain its longevity.

In antiquity, texts were usually read aloud or recited from memory by orators, and so the rule that you “put a comma in whenever you take a breath” can be traced back to the earliest days of reading and writing. Some of the words that we now use to refer to punctuation marks, such as comma, colon and period, originally referred to subparts of a text, differentiating them according to their length and complexity.

Before the arrival of alphabets, ancient texts could not be written out—they were memorized and passed along through an oral tradition. Once texts could be converted into written symbols, they were usually copied down letter for letter—with no punctuation, capitalization or even spacing between words.

Punctuation marks got their start as a way of sorting out the confusion by, for example, breaking material into longer and shorter sections. Back then writers didn’t have to worry about punctuation, which was determined not by the person who composed a work or copied it but by the one who spoke it out loud.

Organized religion, specifically Christianity, played an early role in the development of more formal rules for the use of punctuation. St. Augustine was aghast at the idea that Bible passages might be read incorrectly, and he argued that the placement of punctuation must be in accordance with Church doctrine.

Irish scribes and medieval monks on the European continent also contributed to the development of punctuation. But it was not until the invention of the printing press that punctuation marks became regularized both in their appearance and in their usage. (Modern students, as much as they might labor to learn the proper use of the comma, can take some comfort in knowing that many punctuation marks have simply disappeared and therefore need not be studied.)

Gradually over time a new view of punctuation emerged as the culture shifted from an oral one to a written one and as silent reading become more common than oral declamation. Today there are specific rules for using commas in written texts.

These rules are not based on how a text might be read—either silently or out loud—but rather they are used to divide sentences into smaller units so that they can be understood more quickly and more precisely. The key to applying these rules is to recognize the structural elements of a sentence and how they are joined or separated by commas.

As you can see, the concept of the comma has changed over time and will, no doubt, continue to change. But the long-term trend has been toward greater regularization in developing and applying the rules as well as toward a reduction in the comma's frequency of use. Still the comma remains the most frequently used punctuation mark—and undoubtedly the most frequently misused.

If you want to learn more about the development of punctuation in Western languages, a good book is “Pause and Effect,” by Malcolm B. Parkes. It was published by the University of California Press in 1993 and is the source for most of the information on this page.