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Classification by basic linguistic unit

Several approaches have been taken to classify writing systems, with the most common based on what unit of language is represented by each unit of writing. At the highest level, writing systems are either phonographic (lit. ' sound writing ') when graphemes represent units of sound in a language, or morphographic (lit. ' form writing ') when graphemes represent units of meaning, such as words or morphemes. The term logographic (lit. ' word writing ') is used in various models either as a synonym for "morphographic", or as a specific subtype where the basic unit of meaning written is the word. Even with morphographic writing, there remains a correspondence between graphemes and the sounds of speech, but the pronunciation values of the units of meaning is not what is being encoded firstly by the writing system.

Many classifications are three-fold, with phonographic systems divided into syllabic and alphabetic (or segmental) systems. Syllabaries use symbols called syllabograms to represent syllables or moras. Alphabets use symbols called letters that correspond to spoken phonemes—or more technically to diaphonemes. Alphabets consist of three types: abjads only have letters for consonants, while pure alphabets have letters for both consonants and vowels. Abugidas use characters that correspond to consonant–vowel pairs. David Diringer proposed a five-fold classification of writing systems, comprising pictographic scripts, ideographic scripts, analytic transitional scripts, phonetic scripts, and alphabetic scripts.