A use of pitch and contour in spoken language to nuance words and, in some languages, to distinguish lexical or grammatical meaning. In Chinese, for example, the tones are distinguished by their pitch range (register), duration and contour (shape). All Chinese syllables have a set tone, which distinguishes it and its meaning from another syllable. However, in certain environments tones can change or be modified, while in rapid spoken Chinese a great many unstressed syllables carry no tone at all.