- published: 23 May 2015
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A letter is a grapheme in an alphabetic system of writing, such as the Greek alphabet and its descendants. Letters compose phonemes and each phoneme represents a phone (sound) in the spoken form of the language.
Written signs in other writing systems are best called syllabograms (which denote a syllable) or logograms (which denote a word or phrase).
The term letter, borrowed from Old French lettre, entered Middle English around AD 1200, eventually displacing the native English term bocstaf (i.e. bookstaff). Letter derives ultimately from Latin littera, itself of unknown origin. The Middle English plural lettres could refer to an epistle or written document, reflecting the use of the Latin plural litteræ. Use of the singular letter to refer to a written document emerges in the 14th century.
As symbols that denote segmental speech, letters are associated with phonetics. In a purely phonemic alphabet, a single phoneme is denoted by a single letter, but in history and practice letters often denote more than one phoneme. A pair of letters designating a single phoneme is called a digraph. Examples of digraphs in English include "ch", "sh" and "th". A phoneme can also be represented by three letters, called a trigraph. An example is the combination "sch" in German.
An alphabet is a standard set of letters (basic written symbols or graphemes) which is used to write one or more languages based on the general principle that the letters represent phonemes (basic significant sounds) of the spoken language. This is in contrast to other types of writing systems, such as logographies, in which each character represents a word, morpheme or semantic unit, and syllabaries, in which each character represents a syllable.
A true alphabet has letters for the vowels of a language as well as the consonants. The first true alphabet is believed to be the Greek alphabet, which is a modified form of the Phoenician alphabet. In other types of alphabet either the vowels are not indicated at all, as was the case in the Phoenician alphabet (such systems are known as abjads), or else the vowels are shown by diacritics or modification of consonants, as in the devanagari used in India and Nepal (these systems are known as abugidas or alphasyllabaries).
There are dozens of alphabets in use today, the most common being the Latin alphabet (which was derived from the Greek). Many languages use modified forms of the Latin alphabet, with additional letters formed using diacritical marks. While most alphabets have letters composed of lines (linear writing), there are also exceptions such as the alphabets used in Braille, fingerspelling, and Morse code.