This category contains writing systems where symbols represent consonants, but the symbols (or graphemes) are varied depending on the following vowel. Such systems are distinguished from Category:Syllabary writing systems, in which each symbol represents a consonant and a vowel, or only a vowel, in some cases followed by a consonant or tone, and Category:Abjad writing systems (systems where symbols represent consonants, and vowel marking is absent or optional).
This categorization follows the classification introduced in 1990 by Peter T. Daniels.