Full stop

The full stop (Commonwealth English), period (North American English), or full point . is a punctuation mark used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamation).^[a]

A full stop is frequently used at the end of word abbreviations—in British usage, primarily truncations like Rev., but not after contractions like Revd; in American English, it is used in both cases. It may be placed after an initial letter used to abbreviate a word. It is often placed after each individual letter in acronyms and initialisms (e.g. "U.S.A."). However, the use of full stops after letters in an initialism or acronym is declining, and many of these without punctuation have become accepted norms (e.g., "UK" and "NATO").^[b]

The mark is also used to indicate omitted characters or, in a series as an ellipsis (... or …), to indicate omitted words.

In the English-speaking world, a punctuation mark identical to the full stop is used as the decimal separator and for other purposes, and may be called a point. In computing, it is called a dot.^[2] It is sometimes called a baseline dot to distinguish it from the interpunct (or middle dot).^[2][3]

The full stop symbol derives from the Greek punctuation introduced by Aristophanes of Byzantium in the 3rd century BCE. In his system, there were a series of dots whose placement determined their meaning.

The full stop at the end of a completed thought or expression was marked by a high dot ⟨˙⟩, called the stigmḕ teleía (στιγμὴ τελεία) or "terminal dot". The "middle dot" ⟨·⟩, the stigmḕ mésē (στιγμὴ μέση), marked a division in a thought occasioning a longer breath (essentially a semicolon), while the low dot ⟨.⟩, called the hypostigmḕ (ὑποστιγμή) or "underdot", marked a division in a thought occasioning a shorter breath (essentially a comma).^[4]

In practice, scribes mostly employed the terminal dot; the others fell out of use and were later replaced by other symbols. From the 9th century onwards, the full stop began appearing as a low mark (instead of a high one), and by the time printing began in Western Europe, the lower dot was regular and then universal.^[4]

The name period is first attested (as the Latin loanword peridos) in Ælfric of Eynsham's Old English treatment on grammar. There, it was distinguished from the full stop (the distinctio), and continued the Greek underdot's earlier function as a comma between phrases.^[5] It shifted its meaning, to a dot marking a full stop, in the works of the 16th-century grammarians.^[5]

In 19th-century texts, British English and American English both frequently used the terms period and full stop.^[6][1] The word period was used as a name for what printers often called the "full point", the punctuation mark that was a dot on the baseline and used in several situations. The phrase full stop was only used to refer to the punctuation mark when it was used to terminate a sentence.^[1] This terminological distinction seems to be eroding. For example, the 1998 edition of Fowler's Modern English Usage used full point for the mark used after an abbreviation, but full stop or full point when it was employed at the end of a sentence;^[7] the 2015 edition, however, treats them as synonymous (and prefers full stop),^[8] and New Hart's Rules does likewise (but prefers full point).^[9] The last edition (1989) of the original Hart's Rules (before it became The Oxford Guide to Style in 2002) exclusively used full point.^[10]

Full stops are the most commonly used punctuation marks; analysis of texts indicate that approximately half of all punctuation marks used are full stops.^[11][12]

Full stops indicate the end of sentences that are not questions or exclamations.

It is usual in North American English to use full stops after initials; e.g. A. A. Milne,^[13] George W. Bush.^[14] British usage is less strict.^[15] A few style guides discourage full stops after initials.^[16][17] However, there is a general trend and initiatives to spell out names in full instead of abbreviating them in order to avoid ambiguity.^[18][19][20]

A full stop is used after some abbreviations.^[21] If the abbreviation ends a declaratory sentence there is no additional period immediately following the full stop that ends the abbreviation (e.g. "My name is Gabriel Gama Jr."). Though two full stops (one for the abbreviation, one for the sentence ending) might be expected, conventionally only one is written. This is an intentional omission, and thus not haplography, which is unintentional omission of a duplicate. In the case of an interrogative or exclamatory sentence ending with an abbreviation, a question or exclamation mark can still be added (e.g. "Are you Gabriel Gama Jr.?").^{[citation needed]}

According to the Oxford A–Z of Grammar and Punctuation, "If the abbreviation includes both the first and last letter of the abbreviated word, as in 'Mister' ['Mr'] and 'Doctor' ['Dr'], a full stop is not used."^{[22][better source needed][23]} This does not include, for example, the standard abbreviations for titles such as Professor ("Prof.") or Reverend ("Rev."), because they do not end with the last letter of the word they are abbreviating.

In American English, the common convention is to include the period after all such abbreviations.^[23]

In acronyms and initialisms, the modern style is generally to not use full points after each initial (e.g.: DNA, UK, USSR). The punctuation is somewhat more often used in American English, most commonly with U.S. and U.S.A. in particular. However, this depends much upon the house style of a particular writer or publisher.^[24] As some examples from American style guides, The Chicago Manual of Style (primarily for book and academic-journal publishing) deprecates the use of full points in acronyms, including U.S.,^[25] while The Associated Press Stylebook (primarily for journalism) dispenses with full points in acronyms except for certain two-letter cases, including U.S., U.K., and U.N., but not EU.^[26]

The period glyph is used in the presentation of numbers, either as a decimal separator or as a thousands separator.

In the more prevalent usage in English-speaking countries, as well as in South Asia and East Asia, the point represents a decimal separator, visually dividing whole numbers from fractional (decimal) parts. The comma is then used to separate the whole-number parts into groups of three digits each, when numbers are sufficiently large.

• 1.007 (one and seven thousandths)
• 1,002.007 (one thousand two and seven thousandths)
• 1,002,003.007 (one million two thousand three and seven thousandths)

The more prevalent usage in much of Europe, southern Africa, and Latin America (with the exception of Mexico due to the influence of the United States), reverses the roles of the comma and point, but sometimes substitutes a (thin-)space for a point.

• 1,007 (one and seven thousandths)
• 1.002,007 or 1 002,007 (one thousand two and seven thousandths)
• 1.002.003,007 or 1 002 003,007 (one million two thousand three and seven thousandths)

(To avoid problems with spaces, another convention sometimes used is to use apostrophe signs (') instead of spaces.)

India, Bangladesh, Nepal, and Pakistan follow the Indian numbering system, which utilizes commas and decimals much like the aforementioned system popular in most English-speaking countries, but separates values of one hundred thousand and above differently, into divisions of lakh and crore:

• 1.007 (one and seven thousandths)
• 1,002.007 (one thousand two and seven thousandths)
• 10,02,003.007 (one million two thousand three and seven thousandths, or ten lakh two thousand three and seven thousandths)

In countries that use the comma as a decimal separator, the point is sometimes found as a multiplication sign; for example, 5,2 . 2 = 10,4; this usage is impractical in cases where the point is used as a decimal separator, hence the use of the interpunct: 5.2 · 2 = 10.4. The interpunct is also used when multiplying units in science – for example, 50 km/h could be written as 50 km·h⁻¹ – and to indicate a dot product, i.e. the scalar product of two vectors.

In many languages, an ordinal dot is used as the ordinal indicator. This apply mostly in Central and Northern Europe: in German, Hungarian, several Slavic languages (Czech, Slovak, Slovene, Serbo-Croatian), Faroese, Icelandic, Danish, Norwegian, Finnish, Estonian, Latvian, and also in Basque and Turkish.

The Serbian standard of Serbo-Croatian (unlike the Croatian and Bosnian standards) uses the dot in role of the ordinal indicator only past Arabic numerals, while Roman numerals are used without a dot. In Polish, the period can be omitted if there is no ambiguity whether a given numeral is ordinal or cardinal.

In modern texts, multilevel numbered headings are widely used. E.g. number 2.3.1.5 is a 4th level heading within the chapter 2.

In older literature on mathematical logic, the period glyph used to indicate how expressions should be bracketed (see Glossary of Principia Mathematica).

In computing, the full point, usually called a dot in this context, is often used as a delimiter, such as in DNS lookups, Web addresses, file names and software release versions:

• www.wikipedia.org
• document.txt
• 192.168.0.1
• Chrome 92.0.4515.130

It is used in many programming languages as an important part of the syntax. C uses it as a means of accessing a member of a struct, and this syntax was inherited by C++ as a means of accessing a member of a class or object. Java and Python also follow this convention. Pascal uses it both as a means of accessing a member of a record set (the equivalent of struct in C), a member of an object, and after the end construct that defines the body of the program. In APL it is also used for generalised inner product and outer product. In Erlang, Prolog, and Smalltalk, it marks the end of a statement ("sentence"). In a regular expression, it represents a match of any character. In Perl and PHP, the dot is the string concatenation operator. In the Haskell standard library, it is the function composition operator. In COBOL a full stop ends a statement.

In file systems, the dot is commonly used to separate the extension of a file name from the name of the file. RISC OS uses dots to separate levels of the hierarchical file system when writing path names—similar to / (forward-slash) in Unix-based systems and \ (back-slash) in MS-DOS-based systems and the Windows NT systems that succeeded them.

In Unix-like operating systems, some applications treat files or directories that start with a dot as hidden. This means that they are not displayed or listed to the user by default.

In Unix-like systems and Microsoft Windows, the dot character represents the working directory of the file system. Two dots (..) represent the parent directory of the working directory.

Bourne shell-derived command-line interpreters, such as sh, ksh, and bash, use the dot as a command to read a file and execute its content in the running interpreter. (Some of these also offer source as a synonym, based on that usage in the C-shell.)

Versions of software are often denoted with the style x.y.z (or more), where x is a major release, y is a mid-cycle enhancement release and z is a patch level designation, but actual usage is entirely vendor specific.

The term STOP was used in telegrams in the United States in place of the full stop. The end of a sentence would be marked by STOP; its use "in telegraphic communications was greatly increased during the World War, when the Government employed it widely as a precaution against having messages garbled or misunderstood, as a result of the misplacement or emission [sic] of the tiny dot or period."^[27]

In British English, the words "full stop" at the end of an utterance strengthen it; they indicate that it admits of no discussion: "I'm not going with you, full stop." In American English, the word "period" serves this function.

Another common use in African-American Vernacular English is found in the phrase "And that's on period", which is used to express the strength of the speaker's previous statement, usually to emphasise an opinion.

The International Phonetic Alphabet uses the full stop to signify a syllable break.

In British English, whether for the 12-hour clock or sometimes its 24-hour counterpart, the dot is commonly used and some style guides recommend it when telling time, including those from non-BBC public broadcasters in the UK, the academic manual published by Oxford University Press under various titles,^[28] as well as the internal house style book for the University of Oxford,^[29] and that of The Economist,^[30] The Guardian^[31] and The Times newspapers.^[32] American and Canadian English mostly prefers and uses colons (:) (i.e., 11:15 PM/pm/p.m. or 23:15 for AmE/CanE and 11.15 pm or 23.15 for BrE),^[33] so does the BBC, but only with 24-hour times, according to its news style guide as updated in August 2020.^[34] The point as a time separator is also used in Irish English, particularly by the Raidió Teilifís Éireann (RTÉ), and to a lesser extent in Australian, Cypriot, Maltese, New Zealand, South African and other Commonwealth English varieties outside Canada.

The practice in the United States and Canada is to place full stops and commas inside quotation marks in most styles.^[35] In the British system, which is also called "logical quotation",^[36] full stops and commas are placed according to grammatical sense:^[35][37] This means that when they are part of the quoted material, they should be placed inside, and otherwise should be outside. For example, they are placed outside in the cases of words-as-words, titles of short-form works, and quoted sentence fragments.

• Bruce Springsteen, nicknamed "the Boss," performed "American Skin." (closed or American style)
• Bruce Springsteen, nicknamed "the Boss", performed "American Skin". (logical or British style)
• He said, "I love music." (both)

There is some national crossover. The American style is common in British fiction writing.^[38] The British style is sometimes used in American English. For example, The Chicago Manual of Style recommends it for fields where comma placement could affect the meaning of the quoted material, such as linguistics and textual criticism.^[39][40]

The use of placement according to logical or grammatical sense, or "logical convention", now the more common practice in regions other than North America,^[41] was advocated in the influential book The King's English by Fowler and Fowler, published in 1906. Prior to the influence of this work, the typesetter's or printer's style, or "closed convention", now also called American style, was common throughout the world.

There have been a number of practices relating to the spacing after a full stop. Some examples are listed below:

• One word space ("French spacing"). This is the current convention in most countries that use the ISO basic Latin alphabet for published and final written work, as well as digital media.^[42][43]
• Two word spaces ("English spacing"). It is sometimes claimed that the two-space convention stems from the use of the monospaced font on typewriters, but in fact that convention replicates much earlier typography—the intent was to provide a clear break between sentences.^[44] This spacing method was gradually replaced by the single space convention in published print, where space is at a premium, and continues in much digital media.^[43][45]
• One widened space (such as an em space). This spacing was seen in historical typesetting practices (until the early 20th century).^[46] It has also been used in other typesetting systems such as the Linotype machine^[47] and the TeX system.^[48] Modern computer-based digital fonts can adjust the spacing after terminal punctuation as well, creating a space slightly wider than a standard word space.^[49]

Although the present Greek full stop (τελεία, teleía) is romanized as a Latin full stop^[50] and encoded identically with the full stop in Unicode,