Испан тіліндегі «ll» және «y» дыбыстарының бірігуі

Sound merger of ⟨ll⟩ and ⟨y⟩ in most Spanish dialects

Yeísmo (ɟʝeˈismo; 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 ). It is an example of delateralization. In other words, and represent the same sound when yeísmo is present. The term yeísmo comes from one of the Spanish names for the letter (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 (ʎeˈismo) has been used to refer to the maintenance of the phonemic distinction between and .

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, relleno is pronounced and conllevar 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.

In most of Argentina and Uruguay, the merged sound is pronounced as a voiced postalveolar fricative ; this is referred to as zheísmo. The 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 sound has recently been devoiced to (sheísmo) among younger speakers. Both zheísmo and sheísmo are types of yeísmo, which refers only to the lack of a phonemic distinction between and , not to any particular phonetic realization of the merged phoneme. Comparatively, within the Ecuadorian Sierra region (spanning from the Imbabura to the Chimborazo Provinces, where the pronunciation of /ʎ/ as survives among the majority population of colonial descended mestizos), the sibilant has not merged, as in Argentina and Uruguay; a distinction is also maintained, but with representing , rather than the original Spanish sound, and representing The shift from /ʎ/ to in this region of Ecuador is theorized to have occurred long before the 20th century, and affected both Ecuadorian Spanish and Quechua; historically (through the early 17th century), Spanish speakers in this area had maintained distinctions between , /ʎ/, This three way distinction is still present in the Quechua of more southerly regions, such as the Azuay province, which uses the graphemes <zh>, <ll>, and <y> to distinguish between these phonemes. In the orthography of several Ecuadorian dialects of Quechua, under the influence of the orthography of Ecuadorian Andean Spanish, the grapheme is also used to represent the sound. Parts of Colombia, similarly to the Andean regions of Ecuador, maintain a distinction between representing and representing This type of distinction is found in southern Antioquia Department and the southeast end of Norte de Santander Department. A greater portion of Andean Colombia maintains the distinction between and Overall, Colombia presents great variety with regards to yeísmo. The same shift from to to (to modern ) historically occurred in the development of Old Spanish; this accounts for such pairings as Spanish mujer vs Portuguese mulher, ojo vs olho, hija vs filha and so on.

The distinction between and remains in the Philippines, Andean Ecuador and Peru, Paraguay, both highland and lowland Bolivia, and the northeastern portions of Argentina that border Paraguay. The retention of a distinction between and is more common in areas where Spanish coexists with other languages, either with Amerindian languages, such as Aymara, Quechua, and Guaraní, which, except for Guaraní, themselves possess the phoneme , or in Spain itself in areas with linguistic contact with Catalan and Basque. By 1989, several traditionally non yeísta areas, such as Bogotá and much of Spain and the Canaries, had begun rapidly adopting yeísmo, in the span of little more than a single generation. In areas where yeísmo is variable, is lost more often in rapid and casual speech. There is also an idiolectal correlation between yeísmo and speech rate, with fast speaking individuals being more likely to be yeísta.

Standard Portuguese distinguishes , and Many Brazilian Portuguese speakers merge and , making (verb) and both Some speakers, mainly of the Caipira dialect of Brazil, merge and , making and both Some Caipira speakers distinguish etymological and , pronouncing olho and óleo In standard French, historical turned into , but the spelling was preserved, hence briller (, originally ), Versailles (, originally ). Romanesco and a number of Southern and Central dialects of Italian have or corresponding to standard Italian ; the merger also occurred in many Northern Italian languages, though it is uncommon in regional Italian spoken in the North of the country, where more usually merges with the sequence .

In Hungarian, in most dialects turned into , but the spelling was preserved, hence lyuk In Swedish, turned into in word initial positions, but the spelling was preserved, hence ljus In Cypriot Greek, is often pronounced as , especially by younger speakers. In Standard Modern Greek, it always surfaces as .