> Almost uniquely in the Spanish-speaking world, Castilian /s/ is retroflex, in the sense that it is articulated with the tip of the tongue bent slightly backwards and reaching its point of closest proximity to the roof of the mouth just behind the alveolar ridge. The term ‘retroflex’ in fact covers a range of articulation types, within which the Castilian /s/ can be subclassified as apical alveolar. Many commentators use the ad hoc symbol [s̺] for the Castilian /s/, reserving the bespoke IPA symbol [ʂ] for the subapical category of retroflex sibilant, in which the tongue is retracted even …