toneme

A toneme is a basic unit of tonal phonology that represents an abstract pitch category underlying the tones of a language. Like consonants and vowels, a toneme is a discrete unit used to distinguish meaning, but it operates on the level of pitch rather than segments. In a tone language, syllables are associated with tonemes, and the surface pitch realized on a syllable reflects its underlying toneme, often shaped by phonological processes.

Languages differ in how many tonemes they have. Some systems contrast only two tones, others have three, four, or more. A single toneme can be realized as a surface pitch that is level (high, mid, low) or as a contour that moves within a syllable. Contour realizations may be the direct result of the underlying toneme or of interactions between tonemes across syllable boundaries through processes like tone spreading or sandhi.

Tonemes can mark lexical distinctions, where different tonemes differentiate words, or grammatical distinctions, where tone encodes tense, aspect, mood, or other categories. Tone sandhi and other phonological processes can alter the realized pitch in connected speech, so the surface tones may differ from the underlying tonemes in context.

In linguistic descriptions, tonology analyzes the system of tonemes and their rules. Well-known tone languages include Mandarin, with multiple contour tones, and Yoruba or Igbo, which employ relatively small inventories of high and low tones to distinguish lexical items. The concept of toneme helps separate abstract pitch categories from their phonetic realization.