| style="background: #f2f2f2;" | implosive | b | đ | | | | |- ! rowspan="2" | Fricative | style="background: #f2f2f2;" | voiceless | | | s/ſ | x | | h |- | style="background: #f2f2f2;" | voiced | ꞗ | d | | gi | g/gh | |- ! colspan="2" | Approximant | v/u/o | l | | y/i/ĕ | | |- ! colspan="2" | Rhotic | | colspan="2" | r | | | |} occurs only at the end of a syllable. This symbol, "Latin small letter B with flourish", looks like: . It has a rounded hook that starts halfway up the left side (where the top of the curved part of the b meets the vertical, straight part) and curves about 180 degrees counterclockwise, ending below the bottom-left corner. does not occur at the beginning of a syllable, but can occur at the end of a syllable, where it is notated i or y (with the difference between the two often indicating differences in the quality or length of the preceding vowel), and after and , where it is notated ĕ. This ĕ, and the it notated, have disappeared from the modern language. Note that b and p never contrast in any position, suggesting that they are allophones. The language also has three clusters at the beginning of syllables, which have since disappeared: tl > modern tr bl > modern gi (Northern), tr (Southern) ml > mnh > modern nh Most of the unusual correspondences between spelling and modern pronunciation are explained by Middle Vietnamese. Note in particular: de Rhodes' system has two different b letters, a regular b and a "hooked" b in which the upper section of the curved part of the b extends leftward past the vertical bar and curls down again in a semicircle. This apparently represented a voiced bilabial fricative . Within a century or so, both and had merged as , spelled as v. de Rhodes' system has a second medial glide that is written ĕ and appears in some words with initial d and hooked b. These later disappear. đ was (and still is) alveolar, whereas d was dental. The choice of symbols was based on the dental rather than alveolar nature of and its allophone in Spanish and other Romance languages. The inconsistency with the symbols assigned to vs. was based on the lack of any such place