The question mark (?; also known as an interrogation point, interrogation mark, question point, query or eroteme),[1] is a punctuation mark that replaces the full stop (period) at the end of an interrogative sentence in English and many other languages. The question mark is not used for indirect questions. The question mark character is also often used in place of missing or unknown data.
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According to a 2011 discovery by a Cambridge manuscript expert, Syriac was the first language to use a question mark in the form of a vertical double dot.[2] Lynne Truss attributes an early form of the question mark to Alcuin of York.[3] Truss describes the punctus interrogativus of the late 8th century as "a lightning flash, striking from right to left".[4] (The punctuation system of Aelius Donatus, current through the Early Middle Ages, used only simple dots at various heights.)
This earliest question mark was a decoration of one of these dots, with the "lightning flash" perhaps meant to denote intonation (or a tilde or titlo, named after the Latin word titulus, as in “ ·~ ”, like those wavy and more or less slanted marks used in lots of medieval texts for denoting various things such as abbreviations, and that would become later various diacritics or ligatures or modified letters used in the Latin script), and perhaps associated with early musical notation like neumes.[5][6] Over the next three centuries this pitch-defining element (if it ever existed) seems to have been forgotten, so that the Alcuinesque stroke-over-dot sign (with the stroke sometimes slightly curved) is often seen indifferently at the end of clauses, whether they embody a question or not.
In the early 13th century, when the growth of communities of scholars (universities) in Paris and other major cities led to an expansion and streamlining of the book-production trade,[7] punctuation was rationalised by assigning Alcuin's stroke-over-dot specifically to interrogatives; by this time the stroke was more sharply curved and can easily be recognised as the modern question-mark.
The symbol is also sometimes[8] thought to originate from the Latin quaestiō (that is, qvaestio), meaning "question", which was abbreviated during the Middle Ages to Qo. The uppercase Q was written above the lowercase o, and this mark was transformed into the modern symbol. However, evidence of the actual use of the Q-over-o notation in medieval manuscripts is lacking; if anything, medieval forms of the upper component seem to be evolving towards the q-shape rather than away from it.
In some languages, such as Spanish, typography since the 18th century has required opening and closing question marks,[9] as in "¿Qué hora es?" (What time is it?); an interrogative sentence or phrase begins with an inverted question mark (¿) and ends with the question mark (?). This orthographical rule is often disregarded in quick typing, although its omission is always considered a mistake.
In Armenian the question mark ( ՞ ) takes the form of an open circle and is placed over the last vowel of the question word. It is defined in Unicode at U+055E ՞ armenian question mark.
In Greek and Church Slavonic, the question mark is a semicolon. The regular Latin semicolon can be used U+003B ; semicolon. Although it exists a separate character U+037E ; greek question mark, the regular semicolon is well used.
In Arabic and languages that use Arabic script and were influenced by the Arabic language such as Persian and Urdu, which are written from right to left, the question mark ؟ is mirrored right-to-left from the English question mark. (Some browsers may display the character in the previous sentence as a forward question mark due to font or text directionality issues). Hebrew is also written right-to-left, but it uses a question mark that appears on the page in the same orientation as the Roman-alphabet question mark.[10]
In Unicode, two encodings are available: U+061F ؟ arabic question mark (HTML: ؟ With Bidi code AL: Right-to-Left Arabic) and U+2E2E ⸮ reversed question mark (HTML: ⸮ With bi-directional code Other Neutrals).
The question mark is also used in modern writing in Chinese, Korean, and Japanese, although it is not strictly necessary in Japanese. Usually it is written as fullwidth form in Chinese and Japanese, in Unicode: U+FF1F ？ fullwidth question mark.
Some other scripts have a specific question mark:
French usage must include a white space before the question mark (for example, "Que voulez-vous boire ?").[11]
In typography, some stylistic variants and combinations are available:
The rhetorical question mark or percontation point was invented by Henry Denham in the 1580s and was used at the end of a rhetorical question; however, its use died out in the 17th century. It was the reverse of an ordinary question mark, so that instead of the main opening pointing back into the sentence, it opened away from it.[12] This character can be represented using the reversed question mark (⸮) found in Unicode as U+2E2E. The percontation point is analogous to the Irony mark, but these are very rarely seen.
Rhetorical questions in some (informal) situations can use a bracketed question mark, e.g. "Oh, really(?)", for example in 888 subtitles.[13]
The question mark can also be used as a meta-sign to signal uncertainty regarding what precedes. It is usually put between brackets (?). The uncertainty may concern either a superficial (such as unsure spelling) or a deeper truth (real meaning) level.
In computing, the question mark character is represented by ASCII code 63 (0x3F hexadecimal), and is located at Unicode code-point U+003F. The full-width (double-byte) equivalent, ？, is located at Unicode code point U+FF1F.
The question mark is often utilized as a wildcard character: a symbol that can be used to substitute for any other character or characters in a string. In particular "?" is used as a substitute for any one character as opposed to the asterisk, "*", which can be used as a substitute for zero or more characters in a string. The inverted question mark (¿) corresponds to Unicode code-point 191 (U+00BF), and can be accessed from the keyboard in Microsoft Windows on the default US layout by holding down the Alt key and typing either 1 6 8 (ANSI) or 0 1 9 1 (Unicode) on the numeric keypad. In GNOME applications, it can be entered by typing the hexadecimal Unicode character while holding down both ctrl and shift, i.e.: ctrl+shift+BF. In recent XFree86 and X.Org incarnations of the X Window System, it can be accessed as a compose sequence of two straight question marks, i.e. pressing <Compose> ? ? yields ¿. In the Mac OS, option+shift+? produces an inverted question mark.
The question mark is used in ASCII renderings of the International Phonetic Alphabet, such as SAMPA in place of the glottal stop symbol, ʔ, (which resembles "?" without the dot), and corresponds to Unicode code point U+0294, Latin letter glottal stop.
In computer programming, the symbol "?" has a special meaning in many programming languages. In C-descended languages, "?" is part of the ?: operator, which is used to evaluate simple boolean conditions. In C# 2.0, the "?" modifier and the "??" operator are used to handle nullable data types. In the POSIX syntax for regular expressions, such as the one used in Perl and Python, ? stands for "zero or one instance of the previous subexpression", i.e. an optional element. In certain implementations of the BASIC programming language, the "?" character may be used as a shorthand for the "print" function; in others (notably the BBC BASIC family), "?" is used to address a single-byte memory location. In OCaml, the question mark precedes the label for an optional parameter. In Scheme, as a convention, symbol names ending in ? are used for predicates such as odd?, null?, and eq?. Similarly, in Ruby, method names ending in ? are used for predicates.
In many web browsers and other computer programs, "?" is used to show a character not found in the program's character set. This commonly occurs for apostrophes and quotation marks when they are written with software that uses its own proprietary non-standard code for these characters, such as Microsoft's Smart Quotes. Some fonts will instead use the Unicode Replacement Glyph (U+FFFD, �), which is commonly rendered as a white question mark in a black diamond (see replacement character).
The generic URL syntax allows for a query string to be appended to a resource location in a web address so that additional information can be passed to a script; the query mark, ?, is used to indicate the start of a query string. A query string is usually made up of a number of different field/value pairs, each separated by the ampersand symbol, &, as seen in this url:
http://www.example.com/login.php?username=test&password=blank
Here, a script on the page login.php on the server www.example.com is to provide a response to the query string containing the pairs "username"-"test" and "password"-"blank".
In algebraic chess notation, "?" denotes a bad move, and "??" a blunder, "?!" a dubious move and "!?" an interesting move. For details of all of the chess punctuation see punctuation (chess).
In mathematics, "?" commonly denotes Minkowski's question mark function. In equations, it can mean "questioned" as opposed to "defined".
A question mark is used in English medical notes to suggest a possible diagnosis. It facilitates the recording of a doctor’s impressions regarding a patient’s symptoms and signs. For example, for a patient presenting with left lower abdominal pain, a differential diagnosis might include ?Diverticulitis (read as 'Query Diverticulitis').
