Summary

When the phonological form of a morpheme—a unit of meaning that cannot be decomposed further into smaller units of meaning—involves a particular melodic pattern as part of its sound shape, this morpheme is specified for tone. In view of this definition, phrase- and utterance-level melodies—also known as intonation—are not to be interpreted as instances of tone. That is, whereas the question “Tomorrow?” may be uttered with a rising melody, this melody is not tone, because it is not a part of the lexical specification of the morpheme tomorrow. A language that presents morphemes that are specified with specific melodies is called a tone language. It is not the case that in a tone language every morpheme, content word, or syllable would be specified for tone. Tonal specification can be highly restricted within the lexicon. Examples of such sparsely specified tone languages include Swedish, Japanese, and Ekagi (a language spoken in the Indonesian part of New Guinea); in these languages, only some syllables in some words are specified for tone. There are also tone languages where each and every syllable of each and every word has a specification. Vietnamese and Shilluk (a language spoken in South Sudan) illustrate this configuration. Tone languages also vary greatly in terms of the inventory of phonological tone forms. The smallest possible inventory contrasts one specification with the absence of specification. But there are also tone languages with eight or more distinctive tone categories. The physical (acoustic) realization of the tone categories is primarily fundamental frequency (F0), which is perceived as pitch. However, often other phonetic correlates are also involved, in particular voice quality. Tone plays a prominent role in the study of phonology because of its structural complexity. That is, in many languages, the way a tone surfaces is conditioned by factors such as the segmental composition of the morpheme, the tonal specifications of surrounding constituents, morphosyntax, and intonation. On top of this, tone is diachronically unstable. This means that, when a language has tone, we can expect to find considerable variation between dialects, and more of it than in relation to other parts of the sound system.