Tone

Tone is the use of pitch in language to distinguish lexical or grammatical meaning—that is, to distinguish or to inflect words. All oral languages use pitch to express emotional and other para-linguistic information and to convey emphasis, contrast and other such features in what is called intonation, but not all languages use tones to distinguish words or their inflections, analogously to consonants and vowels.

Sources:

Singh, Chander Shekhar (2004). Punjabi Prosody: The Old Tradition and The New Paradigm. Sri Lanka: Polgasowita: Sikuru Prakasakayo. pp. 70–82.

Kuang, J.-J. (2013). Phonation in Tonal Contrasts (Doctoral dissertation). University of California, Los Angeles.

Trask, R.L. (2 August 2004). A Dictionary of Phonetics and Phonology. Routledge. ISBN 978-1-134-83100-5.

Laver, John; John, Laver (12 May 1994). Principles of Phonetics. Cambridge University Press. pp. 477–478. ISBN 0-521-45655-X.