A syllabary is a set of written symbols that represent the syllables or (more frequently) moras which make up words. In a syllabary, there is no systematic similarity between the symbols which represent syllables with the same consonant or vowel. That is, the symbol for ka does not resemble in any predictable way the symbol for ki, nor the symbol for a.

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 and CV-tone 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.