A diacritic is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek διακριτικός, from διακρίνω. The word diacritic is a noun, though it is sometimes used in an attributive sense, whereas diacritical is only an adjective. Some diacritics, such as the acute ⟨ó⟩, grave ⟨ò⟩, and circumflex ⟨ô⟩, are often called accents. Diacritics may appear above or below a letter or in some other position such as within the letter or between two letters.
The Coptic script is the script used for writing the Coptic language, the most recent development of Egyptian. The repertoire of glyphs is based on the uncial Greek alphabet, augmented by letters borrowed from the Egyptian Demotic. It was the first alphabetic script used for the Egyptian language. There are several Coptic alphabets, as the script varies greatly among the various dialects and eras of the Coptic language.
Greek numerals, also known as Ionic, Ionian, Milesian, or Alexandrian numerals, is a system of writing numbers using the letters of the Greek alphabet. In modern Greece, they are still used for ordinal numbers and in contexts similar to those in which Roman numerals are still used in the Western world. For ordinary cardinal numbers, however, modern Greece uses Arabic numerals.
Upsilon or ypsilon is the twentieth letter of the Greek alphabet. In the system of Greek numerals, Υʹ has a value of 400. It is derived from the Phoenician waw .
In the polytonic orthography of Ancient Greek, the rough breathing character is a diacritical mark used to indicate the presence of an sound before a vowel, diphthong, or after rho. It remained in the polytonic orthography even after the Hellenistic period, when the sound disappeared from the Greek language. In the monotonic orthography of Modern Greek phonology, in use since 1982, it is not used at all.
Han unification is an effort by the authors of Unicode and the Universal Character Set to map multiple character sets of the Han characters of the so-called CJK languages into a single set of unified characters. Han characters are a feature shared in common by written Chinese (hanzi), Japanese (kanji), Korean (hanja) and Vietnamese.
San (Ϻ) was an archaic letter of the Greek alphabet. Its shape was similar to modern M or Mu, or to a modern Greek Sigma (Σ) turned sideways, and it was used as an alternative to Sigma to denote the sound. Unlike Sigma, whose position in the alphabet is between Rho and Tau, San appeared between Pi and Qoppa in alphabetic order. In addition to denoting this separate archaic character, the name San was also used as an alternative name to denote the standard letter Sigma.
In writing and typography, a ligature occurs where two or more graphemes or letters are joined to form a single glyph. Examples are the characters ⟨æ⟩ and ⟨œ⟩ used in English and French, in which the letters ⟨a⟩ and ⟨e⟩ are joined for the first ligature and the letters ⟨o⟩ and ⟨e⟩ are joined for the second ligature. For stylistic and legibility reasons, ⟨f⟩ and ⟨i⟩ are often merged to create ⟨fi⟩ ; the same is true of ⟨s⟩ and ⟨t⟩ to create ⟨st⟩. The common ampersand, ⟨&⟩, developed from a ligature in which the handwritten Latin letters ⟨e⟩ and ⟨t⟩ were combined.
A precomposed character is a Unicode entity that can also be defined as a sequence of one or more other characters. A precomposed character may typically represent a letter with a diacritical mark, such as é. Technically, é (U+00E9) is a character that can be decomposed into an equivalent string of the base letter e (U+0065) and combining acute accent (U+0301). Similarly, ligatures are precompositions of their constituent letters or graphemes.
The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to have developed distinct letters for vowels as well as consonants. In Archaic and early Classical times, the Greek alphabet existed in many local variants, but, by the end of the 4th century BC, the Ionic-based Euclidean alphabet, with 24 letters, ordered from alpha to omega, had become standard throughout the Greek-speaking world and is the version that is still used for Greek writing today.
Unicode has subscripted and superscripted versions of a number of characters including a full set of Arabic numerals. These characters allow any polynomial, chemical and certain other equations to be represented in plain text without using any form of markup like HTML or TeX.
Diacritical marks of two dots¨, placed side-by-side over or under a letter, are used in several languages for several different purposes. The most familiar to English-language speakers are the diaeresis and the umlaut, though there are numerous others. For example, in Albanian, ë represents a schwa. Such diacritics are also sometimes used for stylistic reasons.
Unicode supports several phonetic scripts and notation systems through its existing scripts and the addition of extra blocks with phonetic characters. These phonetic characters are derived from an existing script, usually Latin, Greek or Cyrillic. Apart from the International Phonetic Alphabet (IPA), extensions to the IPA and obsolete and nonstandard IPA symbols, these blocks also contain characters from the Uralic Phonetic Alphabet and the Americanist Phonetic Alphabet.
Unicode equivalence is the specification by the Unicode character encoding standard that some sequences of code points represent essentially the same character. This feature was introduced in the standard to allow compatibility with pre-existing standard character sets, which often included similar or identical characters.
The Unicode Consortium and the ISO/IEC JTC 1/SC 2/WG 2 jointly collaborate on the list of the characters in the Universal Coded Character Set. The Universal Coded Character Set, most commonly called the Universal Character Set, is an international standard to map characters, discrete symbols used in natural language, mathematics, music, and other domains, to unique machine-readable data values. By creating this mapping, the UCS enables computer software vendors to interoperate, and transmit—interchange—UCS-encoded text strings from one to another. Because it is a universal map, it can be used to represent multiple languages at the same time. This avoids the confusion of using multiple legacy character encodings, which can result in the same sequence of codes having multiple interpretations depending on the character encoding in use, resulting in mojibake if the wrong one is chosen.
In Unicode and the UCS, a compatibility character is a character that is encoded solely to maintain round-trip convertibility with other, often older, standards. As the Unicode Glossary says:
A character that would not have been encoded except for compatibility and round-trip convertibility with other standards
Many scripts in Unicode, such as Arabic, have special orthographic rules that require certain combinations of letterforms to be combined into special ligature forms. In English, the common ampersand (&) developed from a ligature in which the handwritten Latin letters e and t were combined. The rules governing ligature formation in Arabic can be quite complex, requiring special script-shaping technologies such as the Arabic Calligraphic Engine by Thomas Milo's DecoType.
A typographic approximation is a replacement of an element of the writing system with another glyph or glyphs. The replacement may be a nearly homographic character, a digraph, or a character string. An approximation is different from a typographical error in that an approximation is intentional and aims to preserve the visual appearance of the original. The concept of approximation also applies to the World Wide Web and other forms of textual information available via digital media, though usually at the level of characters, not glyphs.
