Definition and Examples of Periods: Full Stop

A period ( . ) is a punctuation mark indicating a full stop, placed at the end of declarative sentences as well as after many abbreviations. The period is actually called a full stop in British English, according to R.D. Burchfield in "The New Fowler's Modern English Usage," and is also known as a full point. Rene J. Cappon, author of "The Associated Press Guide to Punctuation," explains that the period may appear small but it has an important function in punctuation:

"The period is a mere dot in the panorama of punctuation, but it packs an impressive punch. Unlike, say, the colon or semicolon, it can bring a sentence to a complete halt."

As Merriam-Webster succinctly defines it: "A period is a point used to mark the end of a declarative sentence or an abbreviation."

History of Usage

The period originated with Greek punctuation in the third century B.C., according to Maria Teresa Cox and Riya Pundir in their article "The Mysterious Disappearance of the Punctuation Dot: An Exploratory Study," published in Fortell: A Journal of Teaching English Literature. The Greeks actually used three different dots at the end of sentences and phrases, say Cox and Pundir:

"A low dot '.' indicated a short breath after a short phrase, a mid-dot '・' meant a longer breath after a longer passage, and a high dot '˙' marked a full stop at the end of a completed thought."

Eventually, with the popularization of block books—books printed from woodcuts in Europe around 1300—engravers disregarded the high and middle dots and retained only the low dot, signifying the end of a sentence. Later, with Johannes Gutenberg's invention of the printing press and movable type in the mid-1400s, printers continued the tradition of using only the low dot as a period. William Caxton, a British merchant, writer, and printer, brought the printing press to England in 1476—along with the low dot, or period.

Cox and Pundir note that some writers and grammarians worry that the period is falling out of favor in the age of texting and electronic mail, in favor of exclamation points, ellipses, line breaks, and emoticons. They note that a 2015 survey conducted by the Department of Psychology at the State University of New York at Binghamton found that only 29 percent of American students were using a full stop, or period, because they consider it to be a "bad way to convey heartfelt emotions."

Purpose

As discussed, the period is used to convey the end of a sentence or abbreviation. But it has other uses. Cappon in "The Associated Press Guide to Punctuation," as well as June Casagrande in her book "The Best Punctuation Book, Period.," describe the period's purpose.

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Using End Punctuation: Periods, Question Marks, and Exclamation Points

By Richard Nordquist

Finality: The period can mark the end of a sentence or sentence fragment, as in "Osama bin Laden has given a good imitation of the devil. To the West, at least." Or in: "Joe works here." "Eat." "Leave now." Casagrande uses the period (.) to mark the end of her book's title, right after the word "period," which is a sentence fragment. She likely does so to add emphasis and convince readers that hers is the final word in punctuation.

Initials and abbreviations: Periods are generally used when there are two letters in the initial, such as U.S., according to "The Associated Press Stylebook." However, styles differ with some style guides, such as The Chicago Manual of Style Online, saying you should omit the periods. Even the AP spells the abbreviation for the United States as US in headlines.

State names: These take a period per AP and other styles when you are not using postal ZIP code abbreviations. So you would have: Ala., Md., and  N.H., where by comparison, the ZIP code abbreviations would omit the periods: AL, MD, and NH.

Abbreviations that end in lowercase letters: Some examples are  Gov., Jr., e.g., i.e., Inc., Mr., and et al.

Mathematics–place value: In mathematics, the period is called a decimal point. For example, in the number 101.25, the number placed to the right of the decimal point—in this case, 25—indicates 25/100 or twenty-five one-hundredths. The period/decimal point is often used with numbers. So, $101.25 would read "101 dollars and 25 cents."

Ellipses: Ellipses—also called ellipses points—are three equally spaced points commonly used in writing or printing to indicate the omission of words in a quotation. They are also known as ellipsis dots or suspension points.

Correct and Incorrect Use

Since printers dropped the use of the high and mid-dot centuries ago, the period has actually been the easiest punctuation mark to understand. But it is far from the easiest to use. Punctuation experts note that writers have long struggled with the rules for correctly placing the period. Casagrande gives these tips on the rules and correct use of the period.

Quotation marks: A period always comes before a closing quotation mark. Right: He said, "Get out." Wrong: He said, "Get out". Note that this rule applies to American English. British English requires that you place the period after the quotation mark.

Single quotation marks: A period always comes before the closing single quotation mark: He said, "Don't call me a 'jerk.' "

Apostrophe: An apostrophe indicates the omission of one or more letters from a word. You do place the period after the apostrophe at the end of a sentence but before the final quote mark: He said, "I know you were just talkin'."

Ellipses (...): The AP says you should treat ellipses as a three-letter word, constructed with three periods and bounded by two spaces, as shown here. If the ellipses come after a complete sentence, however, place a period before the ellipses, such as in Martin Luther King Jr.'s famous words: "I have a dream....I have a dream today." 

Dashes: The dash (—) is a mark of punctuation used to set off a word or phrase after an independent clause or to set off a parenthetical remark, such as words, phrases, or clauses that interrupt a sentence. Never use a period before or after a dash. A correct example of how to use a dash effectively (and omit any periods) would be Colonel David Hunt's quote from his article "On the Hunt" published in the National Review on June 25, 2003: "We can't be politically correct—right or left—in the war on terrorism. Period." Note that the only periods are placed after the end of the first sentence and at the end of the fragment, Period.

Initialism: An initialism is an abbreviation that consists of the first letter or letters of words in a phrase, such as EU (for European Union) and NFL (for National Football League). Omit periods from initialisms. 

Falling Out of Favor?

As discussed, periods are often omitted in text messages. Nonetheless, says Claire Fallon, writing for the Huffington Post in a June 6, 2016, article, "There hasn’t been much evidence that a laissez-faire attitude toward the period is migrating from digital messaging to the broader category of the written word."

However, Richard Lederer and John Shore in "Comma Sense: A Fundamental Guide to Punctuation" argue that writers are more frequently using other punctuation marks when they should be using the simple period:

"Every sentence that's not an exclamation or a question must end with a period. And because people are by and large too proud to ask too many questions and too shy to go around hollering all the time, the vast (not the half-vast) majority of sentences are what are called declarative statements—statements that just say something and therefore end in a period."

Sources

Cappon, Rene J. "The Associated Press Guide To Punctuation." Basic Books, January 2003.

Lederer, Richard. "Comma Sense: A Fun-damental Guide to Punctuation." First edition, St. Martin's Griffin, July 10, 2007.