postalveolar or retroflex flap. In the syllable coda, it varies individually as a fricative, a flap or an approximant, though fricatives are ubiquitous in the Northern and Northeastern regions and all states of Southeastern Brazil but São Paulo and surrounding areas. The total inventory of allophones is rather long, or up to , the latter eight being particularly common, while none of them except archaic , that contrasts with the flap in all positions, may occur alone in a given dialect. Few dialects, such as sulista and fluminense, give preference to voiced allophones; elsewhere, they are common only as coda, before voiced consonants. Additionally, some other languages and variants, such as Haitian Creole and Timorese Portuguese, use velar and glottal fricatives instead of traditional rhotics, too. In Vietnamese, depending on dialect, the rhotic can occur as , or . In modern Mandarin Chinese, the phoneme , which is represented as in Hanyu Pinyin, resembles the rhotics in other languages in realization, thus it can be considered a rhotic consonant. Furthermore, there is also a non-syllabic open vowel (conventional transcription, the exact quality varies) that patterns as in some Germanic languages such as German, Danish and Luxembourgish. It occurs only in the syllable coda. Characteristics In broad transcription rhotics are usually symbolised as unless there are two or more types of rhotic in the same language; for example, most Australian Aboriginal languages, which contrast approximant and trill , use the symbols r and rr respectively. The IPA has a full set of different symbols which can be used whenever more phonetic precision is required: an r rotated 180° for the alveolar approximant, a small capital R for the uvular trill, and a flipped small capital R for the voiced uvular fricative or approximant. The fact that the sounds conventionally classified as "rhotics" vary greatly in both place and manner in terms of articulation, and also in their acoustic characteristics, has led several linguists to investigate what, if anything, they have in common that justifies grouping them together. One suggestion that has been made is that each member of the class of rhotics shares certain properties with other members of the class, but not necessarily the same properties with all; in this case, rhotics have a "family resemblance" with each other rather than a strict set of shared properties. Another suggestion is that rhotics are defined by their behaviour on the sonority