Types of Alphabet
The term "alphabet" is used by linguists and paleographers in a wider and a narrower sense. In the wider sense, an alphabet is a script that is segmental on the phoneme level, that is, that has separate glyphs for individual sounds and not for larger units such as syllables or words. In the narrower sense, some scholars distinguish "true" alphabets from two other types of segmental script, abjads and abugidas. These three differ from each other in the way they treat vowels: Abjads have letters for consonants and leave most vowels unexpressed; abugidas are also consonant-based, but indicate vowels with diacritics to or a systematic graphic modification of the consonants. In alphabets in the narrow sense, on the other hand, consonants and vowels are written as independent letters. The earliest known alphabet in the wider sense is the Wadi el-Hol script, believed to be an abjad, which through its successor Phoenician became the ancestor of or inspiration for all later alphabets; the first alphabet in the narrower sense was the Greek alphabet.
The basic Latin alphabet consists of 26 letters: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y and Z
Examples of present-day abjads are the Arabic and Hebrew scripts; true alphabets include Latin, Cyrillic, and Korean Hangul; and abugidas are used to write Amharic, Hindi, and Thai. The Canadian Aboriginal Syllabics are also an abugida rather than a syllabary as their name would imply, since each glyph stands for a consonant which is modified by rotatation to represent the following vowel. (In a true syllabary, each consonant-vowel combination would be represented by a separate glyph.)
The boundaries between the three types of segmental scripts are not always clear-cut. For example, Iraqi Kurdish is written in the Arabic script, which is normally an abjad. However, in Kurdish, writing the vowels is mandatory, and full letters are used, so the script is a true alphabet. Other languages may use a Semitic abjad with mandatory vowel diacritics, effectively making them abugidas. On the other hand, the Phagspa script of the Mongol Empire was based closely on the Tibetan abugida, but all vowel marks were written after the preceding consonant rather than as diacritic marks. Although short a was not written, as in the Indic abugidas, one could argue that the linear arrangement made this a true alphabet. Conversely, the vowel marks of the Amharic abugida (ironically, the original source of the term "abugida") have been so completely assimilated into their consonants that the modifications are no longer systematic and have to be learned as a syllabary rather than as a segmental script. Even more extreme, the Pahlavi abjad eventually became logographic.
Thus the primary classification of alphabets reflects how they treat vowels. For tonal languages, further classification can be based on their treatment of tone, though there are as yet no names to distinguish the various types. Some alphabets disregard tone entirely, especially when it does not carry a heavy functional load, as in Somali and many other languages of Africa and the Americas. Such scripts are to tone what abjads are to vowels. Most commonly, tones are indicated with diacritics, the way vowels are treated in abugidas. This is the case for Vietnamese (a true alphabet) and Thai (an abugida). In Thai, tone is determined primarily by the choice of consonant, with diacritics for disambiguation. In the Pollard script, an abugida, vowels are indicated by diacritics, but the placement of the diacritic relative to the consonant is modified to indicate the tone. More rarely, a script may have separate letters for tones, as is the case for Hmong and Zhuang. For most of these scripts, regardless of whether letters or diacritics are used, the most common tone is not marked, just as the most common vowel is not marked in Indic abugidas.
Alphabets can be quite small. The Book Pahlavi script, an abjad, had only twelve letters at one point, and may have had even fewer later on. Today the Rotokas alphabet has only twelve letters. (The Hawaiian alphabet is sometimes claimed to be as small, but it actually consists of 18 letters, including the ʻokina and five long vowels.) While Rotokas has a small alphabet because it has few phonemes to represent (just eleven), Book Pahlavi was small because many letters had been conflated, that is, the graphic distinctions had been lost over time, and diacritics were not developed to compensate for this as they were in Arabic, another script that lost many of its distinct letter shapes. For example, a comma-shaped letter represented g, d, y, k, or j. However, such apparent simplifications can perversely make a script more complicated. In later Pahlavi papyri, up to half of the remaining graphic distinctions of these twelve letters were lost, and the script could no longer be read as a sequence of letters at all, but instead each word had to be learned as a whole – that is, they had become logograms as in Egyptian Demotic.
The largest segmental script is probably an abugida, Devanagari. When written in Devanagari, Vedic Sanskrit has an alphabet of 53 letters, including the visarga mark for final aspiration and special letters for kš and jñ, though one of the letters is theoretical and not actually used. The Hindi alphabet must represent both Sanskrit and modern vocabulary, and so has been expanded to 58 with the khutma letters (letters with a dot added) to represent sounds from Persian and English.
The largest known abjad is Sindhi, with 51 letters. The largest alphabets in the narrow sense include Kabardian and Abkhaz (for Cyrillic), with 58 and 56 letters, respectively, and Slovak (for the Latin alphabet), with 46. However, these scripts either count di- and tri-graphs as separate letters, as Spanish does with ch and ll, or uses diacritics like Slovak č. The largest true alphabet where each letter is graphically independent is probably Georgian, with 41 letters.
Syllabaries typically contain 50 to 400 glyphs (though the Múra-Pirahã language of Brazil would require only 24 if it did not denote tone, and Rotokas would require only 30), and the glyphs of logographic systems typically number from the many hundreds into the thousands. Thus a simple count of the number of distinct symbols is an important clue to the nature of an unknown script.
It is not always clear what constitutes a distinct alphabet. French uses the same basic alphabet as English, but many of the letters can carry additional marks, such as é, à, and ô. In French, these combinations are not considered to be additional letters. However, in Icelandic, the accented letters such as á, í, and ö are considered to be distinct letters of the alphabet. Some adaptations of the Latin alphabet are augmented with ligatures, such as æ in Old English and Ȣ in Algonquian; by borrowings from other alphabets, such as the thorn þ in Old English and Icelandic, which came from the Futhark runes; and by modifying existing letters, such as the eth ð of Old English and Icelandic, which is a modified d. Other alphabets only use a subset of the Latin alphabet, such as Hawaiian, or Italian, which only uses the letters j, k, x, y and w in foreign words.