Yeísmo (; literally "Y-ism") is a distinctive feature of certain dialects of the Spanish language, characterized by the loss of the traditional palatal lateral approximant phoneme (written ) and its merger into the phoneme (written ), usually realized as a palatal approximant or affricate. It is an example of delateralization. In other words, and represent the same sound when is present. The term comes from one of the Spanish names for the letter (). Over 90% of Spanish speakers exhibit this phonemic merger. Similar mergers exist in other languages, such as French, Italian, Hungarian, Catalan, Basque, Portuguese or Galician, with different social considerations. Occasionally, the term () has been used to refer to the maintenance of the phonemic distinction between and . Pronunciation Most dialects that merge the two sounds represented by and realize the remaining sound as a voiced palatal approximant , which is much like in English your. However, it sometimes becomes a voiced palatal affricate , sounding somewhat like in English jar, especially when appearing after or or at the beginning of a word. For example, is pronounced and is pronounced or . In dialects where is maintained, its pronunciation involves constriction in both the alveolar or post-alveolar area and in the palatal area. Its duration when between vowels is 20% longer than that of a simple , and the formant transitions to the following vowel are nearly twice as long. Replacing with can thus be considered a type of lenition since it results in a lower degree of closure. and In most of Argentina and Uruguay the merged sound is pronounced as a sibilant ; this is referred to as . The sound itself may have originated in Argentina and Uruguay as an influence of local Amerindian languages on the colonial pronunciation of the Spanish language typical of the area's inhabitants of that time, a pronunciation that persisted after the mass immigration of post-colonial Italians and Spaniards into the region which otherwise transformed the demographics and affected aspects of the Spanish language there, including most noticeably intonation. Prior to this post-colonial mass immigration wave, as most other South American countries, their populations were similarly composed of a mestizo majority (those of mixed Spaniard and Amerindian ancestry). In Buenos Aires the sound has recently been devoiced to () among younger speakers. In the Ecuadorian Sierra region spanning from the Imbabura province to the Chimborazo Province, by contrast,