[…] tonemes have a distinctive function in differentiating distinct predicates consisting of the same segmental material. In languages having such tonemic differences, these will have to be coded in the form of the predicate in the lexicon.
- Dik (1989), a pag.387

Tonemes can be distinguished into “level tones” (e.g. High, Low, Mid) and “contour tones”, in which there is a change in pitch level; contour tones may be “simple” (e.g. a Rise, a Fall) or “complex” ( e.g. a Rise-Fall, or a Fall-Rise).
- Dik (1989), a pag.380