Tone contours are numbers that represent the way pitch varies over a syllable. Their invention is attributed Yuen Ren Chao. If you visualise a stave of music, there are five horizontal lines. Each representing a different pitch level. The pitch levels are numbered from 1 to 5, the lowest being 1 and the highest being 5.

The Standard Mandarin third tone has a tone contour /214/, showing a pitch that dips and then rises.

Examples of level tone contours are /11/, /22/, /33/, /44/ and /55/.

Falling tone contours include /51/, /31/, /53/, etc.

Rising tone contours include /13/, /35/, /15/, etc.