Full stop


The full stop, period, or full point, is a punctuation mark used for several purposes, most often to mark the end of a declarative sentence.
A full stop is frequently used at the end of word abbreviations—in British usage, primarily truncations such as Rev., but not after contractions which retain the final letter such as 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 initialisms,, but not usually in those that are acronyms. However, the use of full stops after letters in initialisms is declining, and many of these without punctuation have become accepted norms. When used in a series the mark is also used 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. It is sometimes called a baseline dot to distinguish it from the interpunct.

History

Ancient Greek origin

The full stop symbol derives from the Greek punctuation introduced by Aristophanes of Byzantium in the 3rd century BCE in Alexandria. In his system, there was a series of dots whose placement determined their meaning. His three punctuations were these: the end of a completed thought or expression was marked by a high dot, called the stigmḕ teleía or "terminal dot"; the "middle dot", the stigmḕ mésē, marked a division in a thought occasioning a longer breath ; the low dot, called the hypostigmḕ or "underdot", marked a division in a thought occasioning a shorter breath.
The name period is first attested in Ælfric of Eynsham's Old English treatment on grammar. There, it was distinguished from the full stop and continued the Greek underdot's earlier function as a comma between phrases. It shifted its meaning to a dot marking a full stop in the works of the 16th-century grammarians. In the 7th century, Isidore of Seville updated the system slightly; he assigned the dots to indicate short, medium and long pauses in reading, respectively.

Medieval Latin to modern English

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, and by the time printing began in Western Europe, the lower dot was regular and then universal.
In 19th-century texts, British English and American English both frequently used the terms period and full stop. 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. 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; the 2015 edition, however, treats them as synonymous, and New Hart's Rules does likewise. The last edition of the original Hart's Rules exclusively used full point.

Usage

Full stops are the most commonly used punctuation marks; analysis of texts indicate that approximately half of all punctuation marks used are full stops. Some of the usages of full stops are:

Ending sentences

Full stops indicate the end of declarative sentences, in contrast to questions or exclamations. The full stop is omitted when adjacent to an ellipsis.

Abbreviations

It is usual in North American English to use full stops after initials; e.g.: A. A. Milne and George W. Bush. British usage is less strict. A few style guides discourage full stops after initials. However, there is a general trend and initiatives to spell out names in full instead of abbreviating them in order to avoid ambiguity.
A full stop is used after some abbreviations. If the abbreviation ends a declaratory sentence, there is no additional period immediately following the full stop that ends the abbreviation. Though two full stops might be expected, conventionally only one is written. This is an intentional omission, and thus not haplography, which is an 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.
According to the Oxford Dictionaries, this does not include, for example, the standard abbreviations for titles such as Professor or Reverend, 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.

Acronyms and initialisms

In acronyms and initialisms, the modern style is generally to not use full points after each initial. The punctuation is somewhat more often used in American English, most commonly with U.S. and U.S.A. in particular, depending upon the house style of a particular writer or publisher. As some examples from American style guides, The Chicago Manual of Style deprecates the use of full points in initialisms, including U.S., while The Associated Press Stylebook dispenses with full points in initialisms, including acronyms, except for certain two-letter cases, including U.S., U.K. and U.N., but not EU. Acronyms, which can be pronounced as words, have tended to lose full stops even when they were formerly used; e.g., Queensland and Northern Territory Aerial Services became Q.A.N.T.A.S., then QANTAS, and ultimately Qantas.

Time

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, as well as the internal house style book for the University of Oxford, and that of The Economist, The Guardian and The Times newspapers. American and Canadian English mostly prefers and uses colons ; the UK BBC uses only 24-hour times with a colon, since at least the August 2020 update of its news style guide. The point as a time separator is also used in Irish English, particularly by the , and to a lesser extent in Australian, Cypriot, Maltese, New Zealand, South African and other Commonwealth English varieties outside Canada.

In conversation

In British English, the words "full stop" at the end of an utterance strengthen it; they indicate that it admits no further 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.

Decimal or thousands separator

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 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
  • 1,002.007
  • 1,002,003.007
The more prevalent usage in much of Europe, southern Africa and Latin America reverses the roles of the comma and point but sometimes substitutes a space for a point.
  • 1,007
  • 1.002,007 or 1 002,007
  • 1.002.003,007 or 1 002 003,007
To avoid problems with the 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
  • 1,002.007
  • 10,02,003.007

    Multiplication sign

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.

Ordinal dot

In many languages, an ordinal dot is used as the ordinal indicator. This applies mostly in Central and Northern Europe: in German, Hungarian, several Slavic languages, Faroese, Icelandic, Danish, Norwegian, Finnish, Estonian, Latvian and also in Basque and Turkish. The dots are typically placed after the ordinal number; for example, "7." generally represents the seventh.
The Serbian standard of Serbo-Croatian uses the dot in the 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 about whether a given numeral is ordinal or cardinal.

Multilevel numbered headings

In modern texts, multilevel numbered headings are widely used. For example, the string "2.3.1.5" represents a 4th-level heading within chapter 2.

Logic

In older literature on mathematical logic, the period glyph was used to indicate how expressions should be bracketed, as explained in the Glossary of Principia Mathematica. Full stops can be used as the border of logical operations to potentially prevent ambiguities; e.g., in ⊢: P∈Ω. E!B̌P. ⊃. P∈Ded., full stops are used to separate logical statements.