Spoken Chinese phonology

The usual unit of analysis is the syllable, traditionally analysed as consisting of an initial consonant, a final and a tone. In general, southern varieties have fewer initial consonants than northern and central varieties, but more often preserve the Middle Chinese final consonants. Some varieties, such as Cantonese and the Shanghai dialect, include syllabic nasals as independent syllables.

Initials
In the 42 varieties surveyed in the Great Dictionary of Modern Chinese Dialects, the number of initials (including a zero initial) ranges from 15 in some southern dialects to a high of 35 in the dialect of Chongming Island, Shanghai.

The initial system of the Fuzhou dialect of northern Fujian is a minimal example. With the exception of /ŋ/, which is often merged with the zero initial, the initials of this dialect are present in all Chinese varieties, although several varieties do not distinguish /n/ from /l/. However, most varieties have additional initials, due to a combination of innovations and retention of distinctions from Middle Chinese. Most non-Min varieties have a labio-dental fricative /f/, which developed from Middle Chinese bilabial stops in certain environments. The voiced initials of Middle Chinese are retained in Wu dialects such as Suzhou and Shanghai, as well as Old Xiang dialects, but have merged with voiceless initials elsewhere. The Middle Chinese retroflex initials are retained in many Mandarin dialects, including Beijing but not southwestern and southeastern Mandarin varieties. In many northern and central varieties there is palatalization of dental affricates or velars (or both).

Finals
Chinese finals may be analysed as an optional medial glide, a main vowel and an optional coda.

Conservative vowel systems, such as those of Gan and Hakka dialects, have high vowels /i/, /u/ and /y/, which also function as medials, mid vowels /e/ and /o/, and a low /a/-like vowel. In other dialects, including Mandarin dialects, /o/ has merged with /a/, leaving a single mid vowel with a wide range of allophones. Many dialects, particularly in northern and central China, have apical or retroflex vowels, which are syllabic fricatives derived from high vowels following sibilant initials. In many Wu dialects, vowels and final glides have monophthongized, producing a rich inventory of vowels in open syllables. Reduction of medials is also common in Yue dialects.

The Middle Chinese codas, consisting of glides /j/ and /w/, nasals /m/, /n/ and /ŋ/, and stops /p/, /t/ and /k/, are best preserved in southern dialects, particularly Yue dialects. In Jin, Lower Yantze Mandarin and Wu dialects, the stops have merged as a final glottal stop, while in most northern varieties they have disappeared. In Mandarin dialects final /m/ has merged with /n/, while some central dialects have a single nasal coda, in some cases realized as a nasal vowel.

Tones
All varieties of Chinese, like neighbouring languages in the Mainland Southeast Asia linguistic area, have phonemic tones. Each syllable may be pronounced with between three and six distinct pitch contours, denoting different morphemes. The number of tonal contrasts varies between dialects, with northern dialects tending to have fewer distinctions than southern ones. For example, in the standard language the four phonemic tones can be demonstrated with mā (妈 "mother"), má (麻 "hemp"), mǎ (马 "horse") and mà (骂 "to scold"). Many dialects have tone sandhi, in which the pitch contour of a syllable is affected by the tones of adjacent syllables in a compound word of phrase. This process is so extensive in Shanghainese that the tone system is reduced to a pitch accent system much like modern Japanese.

The tonal categories of modern varieties can be related by considering their derivation from the tones of Middle Chinese, though cognate tonal categories in different dialects are often realized as quite different pitch contours. Middle Chinese had a three-way tonal contrast on all syllables except those ending in stops. The traditional names of the tonal categories are "level" (平 píng), "rising" (上 shǎng), and "departing" (去 qù). Syllables ending in a stop consonant, or  (checked syllables) had no tonal contrasts but were traditionally treated as a fourth tone category, "entering" (入 rù), corresponding to syllables ending in nasals , , or.

The tones of Middle Chinese, as well as similar systems in neighbouring languages, experienced a tone split conditioned by syllabic onsets. Syllables with voiced initials tended to be pronounced with a lower pitch, and by the late Tang Dynasty, each of the tones had split into two registers conditioned by the initials, known as the "upper", or 阴/陰 (yīn), and the "lower", or 阳/陽 (yáng). When voicing was lost in all dialects except the Wu and Old Xiang groups, this distinction became phonemic, yielding eight tonal categories, with a six-way contrast in unchecked syllables and a two-way contrast in checked syllables. Cantonese maintains these tones and has developed an additional distinction in checked syllables. However, most varieties have reduced the number of tonal distinctions. For example, in Mandarin, the tones resulting from the split of Middle Chinese rising and departing tones merged, leaving four tones. Furthermore, final stop consonants disappeared in most Mandarin dialects, and such syllables were reassigned to one of the other four tones.

In Wu, voiced obstruents were retained, and the tone split never became phonemic: the higher-pitched allophones occur with initial voiceless consonants, and the lower-pitched allophones occur with initial voiced consonants. (Traditional Chinese classification nonetheless counts these as different tones.) Most Wu dialects retain the tone categories of Middle Chinese, but in Shanghainese several of these have merged.

Many Chinese varieties exhibit tone sandhi, in which the realization of a tone varies depending on the context of the syllable. For example, in Standard Chinese a third tone changes to a second tone when followed by another third tone. Particularly complex sandhi patterns are found in Wu dialects and coastal Min dialects. In Shanghainese, the tone of all syllables in a word is determined by the tone of the first, so that Shanghainese has word rather than syllable tone.