flap (these terms describe very similar articulations): Similar to a trill, but involving just one brief interruption of airflow. In many languages flaps are used as reduced variants of trills, especially in fast speech. However, in Spanish, for example, flaps and trills contrast, as in pero ("but") versus perro ("dog"). Also flaps are used as basic rhotics in Japanese and Korean languages. In Australian English and most American dialects of English, taps do not function as rhotics but are realizations of intervocalic apical stops ( and , as in rider and butter). The IPA symbol for these sounds is (or substandard for the tap, contrasted with the flap ). Alveolar or retroflex approximant (as in most accents of English—with minute differences): The front part of the tongue approaches the upper gum, or the tongue-tip is curled back towards the roof of the mouth ("retroflexion"). No or little friction can be heard, and there is no momentary closure of the vocal tract. The IPA symbol for the alveolar approximant is and the symbol for the retroflex approximant is . There is a distinction between an unrounded retroflex approximant and a rounded variety that probably could have been found in Anglo-Saxon and even to this day in some dialects of English, where the orthographic key is r for the unrounded version and usually wr for the rounded version (these dialects will make a differentiation between right and write). Also used as a rhotic in some dialects of Armenian, Dutch, German, Brazilian Portuguese (depending on phonotactics). Uvular (popularly called guttural r): The back of the tongue approaches the soft palate or the uvula. The standard Rs in European Portuguese, French, German, Danish, and Modern Hebrew are variants of this rhotic. If fricative, the sound is often impressionistically described as harsh or grating. This includes the voiced uvular fricative, voiceless uvular fricative, and uvular trill. In northern England, there were accents that once employed a uvular R, which was called a "burr". developmental non-rhotic Rs: Many non-rhotic British speakers have a labialization to of their Rs, which is between idiosyncratic and dialectal (southern and southwestern England), and since it includes some RP speakers, somewhat prestigious. Apart from English, in all Brazilian Portuguese dialects the phoneme, or , may be actually realized as other, traditionally non-rhotic, fricatives (and most often is so), unless it occurs single between vowels, being so realized as a dental, alveolar,