The Greek alphabet is the script that has been used to write the Greek language since the 8th century BC. It was derived from the earlier Phoenician alphabet, and was in turn the ancestor of numerous other European and Middle Eastern scripts, including Cyrillic and Latin. Apart from its use in writing the Greek language, both in its ancient and its modern forms, the Greek alphabet today also serves as a source of technical symbols and labels in many domains of mathematics, science and other fields.
In its classical and modern form, the alphabet has 24 letters, ordered from alpha to omega. Like Latin and Cyrillic, Greek originally had only a single form of each letter; it developed the letter case distinction between upper-case and lower-case forms in parallel with Latin during the modern era.
Sound values and conventional transcriptions for some of the letters differ between Ancient Greek and Modern Greek usage, owing to phonological changes in the language.
In traditional ("polytonic") Greek orthography, vowel letters can be combined with several diacritics, including accent marks, so-called "breathing" marks, and the iota subscript. In common present-day usage for Modern Greek since the 1980s, this system has been simplified to a so-called "monotonic" convention.
A writing system is an organized regular method (typically standardized) of information storage and transfer for the communication of messages (expressing thoughts or ideas) in a language by visually (or possibly tactilely) encoding and decoding (known as writing and reading) with a set of signs or symbols, both known generally as characters (with the set collective referred to as a 'script'). These characters, often including letters and numbers, are usually recorded onto a durable medium such as paper or electronic storage/display, although non-durable methods may also be used, such as writing in sand or skywriting.
The general attributes of writing systems can be placed into broad categories such as alphabets, syllabaries, or logographies. Any particular system can have attributes of more than one category. In the alphabetic category, there is a standard set of letters (basic written symbols or graphemes) of consonants and vowels that encode based on the general principle that the letters (or letter pair/groups) represent phonemes (basic significant sounds) of the spoken language. A syllabary typically correlates a symbol to a syllable (which can be a pairing or group of phonemes, and are considered the building blocks of words). In a logography, each character represents a word, morpheme or semantic unit (which themselves can be pairings or groups of syllables). Other categories include abjads (which is an alphabet where vowels are not indicated at all) and abugidas, also called alphasyllabaries (where vowels are shown by diacritics or other modification of consonants). A system's category can often be determined just by identifying the number of symbols used within the system. Alphabets typically use a set of 20-to-35 symbols to fully express a language, whereas syllabaries can have 80-to-100, and logographies can have several hundreds of symbols.