Period mark

The full stop (Commonwealth English), period (North American English), or full point , is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamation). This sentence-ending use, alone, defines the strictest sense of ''full stop''. Although ''full stop'' technically applies only when the mark is used to end a sentence, the distinction – drawn since at least 1897 – is not maintained by all modern style guides and dictionaries.

The mark is also used, singly, to indicate omitted characters or, in a series, as an ellipsis (), to indicate omitted words. It may be placed after an initial letter used to stand for a name or after each individual letter in an initialism or acronym (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"). This trend has progressed somewhat more slowly in the United States than in other English language dialects.

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).

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 (or middle dot).

History

Ancient Greek origin

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

''stigmḕ teleía'', ''stigmḕ mésē'' and ''hypostigmḕ''

The full stop at 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 (essentially a semicolon), while the low dot ⟨.⟩, called the ''hypostigmḕ'' () or "underdot", marked a division in a thought occasioning a shorter breath (essentially a comma).

Medieval simplification

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.

Medieval Latin and modern English ''period''

The name ''period'' is first attested (as the Latin loanword ) in Ælfric of Eynsham's Old English treatment on grammar. There, it is distinguished from the full stop (the ), and continues the Greek underdot's earlier function as a comma between phrases.''Oxford English Dictionary'', "period, ''n.'', ''adj.'', and ''adv.''" Oxford University Press, 2005, It shifted its meaning, to a dot marking a full stop, in the works of the 16th-century grammarians. In 19th-century texts, both British English and American English were consistent in their usage of 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 prefers ''full stop''), and ''New Hart's Rules'' does likewise (but prefers ''full point''). Essentially the same text is found in the previous edition under various titles, including ''New Hart's Rules'', ''Oxford Style Manual'', and ''The Oxford Guide to Style''. In 1989, the last edition (1989) of the original ''Hart's Rules'' (before it became '' The Oxford Guide to Style'' in 2002) 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.

Ending sentences

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

After initials

It is usual in North American English to use full stops after initials; e.g. A. A. Milne, 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.

Abbreviations

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 (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.?").

Abbreviations and personal titles of address

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." 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.

Acronyms and initialisms

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. 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.'', 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''.

Mathematics

The period glyph is used in the presentation of numbers, but in only one of two alternate styles at a time.

In the more prevalent usage in English-speaking countries, 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. This notation is also seen when multiplying units in science; for example, 50 km/h could be written as 50 km·h⁻¹. However, the point is used in all countries to indicate a dot product, i.e. the scalar product of two vectors.

Logic

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

Computing

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.

Telegraphy

The term ''STOP'' was used in telegrams 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 of the tiny dot or period."

In conversation

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.

Linguistics

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

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
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