Tone pattern in the context of "Du Fu"

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. Languages that have this feature are called tonal languages; the distinctive tone patterns of such a language are sometimes called tonemes, by analogy with phoneme. Tonal languages are common in East and Southeast Asia, Africa, the Americas, and the Pacific.

Tonal languages are different from pitch-accent languages in that tonal languages can have each syllable with an independent tone whilst pitch-accent languages may have one syllable in a word or morpheme that is more prominent than the others.

The four tones of Chinese poetry and dialectology (simplified Chinese: 四声; traditional Chinese: 四聲; pinyin: sìshēng) are four traditional tone classes of Chinese words. They play an important role in Chinese poetry and in comparative studies of tonal development in the modern varieties of Chinese, both in traditional Chinese and in Western linguistics. They correspond to the phonology of Middle Chinese, and are named even or level (平 píng), rising (上 shǎng), departing or going (去 qù), and entering or checked (入 rù). (The last three are collectively referred to as oblique 仄 (zè), an important concept in poetic tone patterns.) They are reconstructed as mid (˧ or 33), mid rising (˧˥ or 35), high falling (˥˩ or 51), and mid (˧ or 33) with a final stop consonant respectively. Due to historic splits and mergers, none of the modern varieties of Chinese have the exact four tones of Middle Chinese, but they are noted in rhyming dictionaries.