A syllabary is a set of written symbols that represent the syllables or (more frequently) moras which make up words. A symbol in a syllabary, called a syllabogram, typically represents an (optional) consonant sound (simple onset) followed by a vowel sound (nucleus)--that is, a CV or V syllable--but other phonographic mappings such as CVC, CV- tone, and C (normally nasals at the end of syllables) are also found in syllabaries.
A writing system using a syllabary is complete when it covers all syllables in the corresponding spoken language without requiring complex orthographic / graphemic rules, like implicit codas (⟨C1V⟩ => /C1VC2/) silent vowels (⟨C1V1+C2V2⟩ => /C1V1C2/) or echo vowels (⟨C1V1+C2V1⟩ => /C1V1C2/). This loosely corresponds to shallow orthographies in alphabetic writing systems.
True syllabograms are those that encompass all parts of a syllable, i.e. initial onset, medial nucleus and final coda, but since onset and coda are optional in at least some languages, there are middle (nucleus), start (onset-nucleus), end (nucleus-coda) and full (onset-nucleus-coda) true syllabograms. Most syllabaries only feature one or two kinds of syllabograms and form other syllables by graphemic rules.
Syllabograms, hence syllabaries, are pure, analytic or arbitrary if they do not share graphic similarities that correspond to phonic similarities, e.g. the symbol for ka does not resemble in any predictable way the symbol for ki, nor the symbol for a. Otherwise they are synthetic, if they vary by onset, rime, nucleus or coda, or systematic, if they vary by all of them. Some scholars, e.g. Daniels, reserve the general term for analytic syllabaries and invent other terms (abugida, abjad) as necessary. Some system provides katakana language conversion.
Languages that use syllabic writing include Japanese, Cherokee, Vai, the Yi languages of eastern Asia, the English-based creole language Ndyuka, Shaozhou Tuhua, and the ancient language Mycenaean Greek (Linear B). In addition, the undecoded Cretan Linear A is also believed by some to be a syllabic script, though this is not proven.
Chinese characters, the cuneiform script used for Sumerian, Akkadian and other languages, and the former Maya script are largely syllabic in nature, although based on logograms. They are therefore sometimes referred to as logosyllabic.
The contemporary Japanese language uses two syllabaries together called kana, namely hiragana and katakana, which were developed around 700. Because Japanese uses mainly CV (consonant + vowel) syllables, a syllabary is well suited to write the language. As in many syllabaries, vowel sequences and final consonants are written with separate glyphs, so that both atta and kaita are written with three kana: (a-t-ta) and (ka-i-ta). It is therefore sometimes called a moraic writing system.
Languages that use syllabaries today tend to have simple phonotactics, with a predominance of monomoraic (CV) syllables. For example, the modern Yi script is used to write languages that have no diphthongs or syllable codas; unusually among syllabaries, there is a separate glyph for every consonant-vowel-tone combination (CVT) in the language (apart from one tone which is indicated with a diacritic).
Few syllabaries have glyphs for syllables that are not monomoraic, and those that once did have simplified over time to eliminate that complexity. For example, the Vai syllabary originally had separate glyphs for syllables ending in a coda (do?), a long vowel (soo), or a diphthong (bai), though not enough glyphs to distinguish all CV combinations (some distinctions were ignored). The modern script has been expanded to cover all moras, but at the same time reduced to exclude all other syllables. Bimoraic syllables are now written with two letters, as in Japanese: diphthongs are written with the help of V or hV glyphs, and the nasal coda is written with the glyph for ?, which can form a syllable of its own in Vai.
In Linear B, which was used to transcribe Mycenaean Greek, a language with complex syllables, complex consonant onsets were either written with two glyphs or simplified to one, while codas were generally ignored, e.g. ko-no-so for Kn?sos, pe-ma for sperma.
The Cherokee syllabary generally uses dummy vowels for coda consonants, but also has a segmental grapheme for /s/, which can be used both as a coda and in an initial /sC/ consonant cluster.
The languages of India and Southeast Asia, as well as the Ethiopian Semitic languages, have a type of alphabet called an abugida or alphasyllabary. In these scripts, unlike in pure syllabaries, syllables starting with the same consonant are generally expressed with graphemes based in a regular way on a common graphical element. Usually each character representing a syllable consists of several elements which designate the individual sounds of that syllable.
In the 19th century these systems were called syllabics, a term which has survived in the name of Canadian Aboriginal syllabics (also an abugida).
In a true syllabary there may be graphic similarity between characters that share a common consonant or vowel sound, but it is not systematic or at all regular. For example, the characters for 'ke', 'ka', and 'ko' in Japanese hiragana have no similarity to indicate their common "k" sound (these being, ? and ?). Compare this with Devanagari, an abugida, where the characters for 'ke', 'ka' and 'ko' are , and respectively, with ? indicating their common "k" sound.
English, along with many other Indo-European languages like German and Russian, allows for complex syllable structures, making it cumbersome to write English words with a syllabary. A "pure" syllabary would require a separate glyph for every syllable in English. Thus one would need separate symbols for "bag", "beg", "big", "bog", "bug", "bad", "bed", "bid", "bod", "bud", "bead", "bide", "bode", etc. Since English has well over 10,000 different possibilities for individual syllables, a syllabary would be poorly suited to represent the English language. However, such pure systems are rare. A work-around to this problem, common to several syllabaries around the world (including English loanwords in Japanese), is to write an echo vowel, as if the syllable coda were a second syllable: ba-gu for "bag", etc. Another common approach is to simply ignore the coda, so that "bag" would be written ba. This obviously would not work well for English, but was done in Mycenaean Greek when the root word was two or three syllables long and the syllable coda was a weak consonant such as n or s (example: chrysos written as ku-ru-so).