Yeísmo

Yeísmo (Spanish pronunciation: [ɟʝeˈismo]; literally "Y-ism") is a distinctive feature of many dialects of the Spanish language, characterized by the loss of the traditional palatal lateral approximant phoneme /ʎ/ ^ⓘ (written ⟨ll⟩) and its merger into the phoneme /ʝ/ ^ⓘ (written ⟨y⟩). It is an example of delateralization.

In other words, ⟨ll⟩ and ⟨y⟩ represent the same sound [ʝ] ^ⓘ when yeísmo is present. The term yeísmo comes from one of the Spanish names for the letter ⟨y⟩ (ye). 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 lleísmo (pronounced [ʎeˈismo]) has been used to refer to the maintenance of the phonemic distinction between /ʝ/ and /ʎ/.

Most dialects that merge the two sounds represented by ⟨ll⟩ and ⟨y⟩ realize the remaining sound as a voiced palatal fricative [ʝ] ^ⓘ, which is much like ⟨y⟩ in English your. However, it sometimes becomes a voiced palatal affricate [ɟʝ] ^ⓘ, sounding somewhat like ⟨j⟩ in English jar, especially when appearing after /n/ or /l/ or at the beginning of a word. For example, relleno is pronounced [reˈʝeno] and conllevar is pronounced [koɲɟʝeˈβaɾ] or [kondʒeˈβaɾ].

In dialects where /ʎ/ 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 /l/, and the formant transitions to the following vowel are nearly twice as long. Replacing /ʎ/ with /ʝ/ can thus be considered a type of lenition since it results in a lower degree of closure.

In most of Argentina and Uruguay, the merged sound is pronounced as a voiced postalveolar fricative [ʒ]; this is referred to as zheísmo.

The [ʒ] sound itself may have originated in Argentina and Uruguay as an influence from the local Amerindian languages on the colonial Spanish spoken by the area's inhabitants of that time; the pronunciation then persisted after the mass immigration of post-colonial Italians, Germans, Spaniards and more into the region, which effectively transformed the region's demographics and affected various aspects of the Spanish language there, including (most noticeably) intonation. Prior to this post-colonial mass immigration wave, like most other South American countries, the populations of Argentina and Uruguay were similarly composed of a mestizo majority (those of mixed Spaniard and Amerindian ancestry); in Buenos Aires, the [ʒ] sound has recently been devoiced to [ʃ] (sheísmo) among younger speakers.

Both zheísmo and sheísmo are types of yeísmo, which refers only to the lack of a phonemic distinction between /ʎ/ and /ʝ/, not to any particular phonetic realization of the merged phoneme.