Yeísmo (Spanish pronunciation: [ɟ͡ʝeˈizmo]) is a distinctive feature of many dialects of the Spanish language, which consists of the loss of the traditional palatal lateral approximant phoneme /ʎ/ (written ⟨ll⟩) and its merger into the phoneme /ʝ/ (written ⟨y⟩), usually realized as a palatal approximant or affricate. In other words, ⟨ll⟩ and ⟨y⟩ represent the same sound /ʝ/. The term yeísmo comes from the Spanish name of the letter ⟨y⟩ (ye). The opposite term is lleísmo (pronounced: [ʎeˈizmo]), which is attested sparingly in some fewer subvarieties, and refers to the distinction of /ʝ/ (spelled "y") and /ʎ/ (spelled "ll").
Most dialects currently realize the merged phoneme as a voiced palatal fricative or approximant [ʝ] or [j]. For example, relleno [reˈʝeno, reˈjeno], eyectar [eʝeɣˈtaɾ, ejeɣˈtaɾ]. This same merged phoneme becomes an affricate or a plosive (either a voiced postalveolar affricate [dʒ] as in English jar, a voiced palatal affricate [ɟ͡ʝ], or a voiced palatal stop [ɟ]), after a nasal (as in the words cónyuge, conllevar), after a lateral (as in el yunque, el llano), and commonly after a pause.
Extent of yeísmo and lleísmo 
Yeísmo has always been common in much of Latin America, mainly in lowlands, and also in large areas in Spain. The distinction is particularly more common in areas where bilingualism with other languages that have a similar distinction, such as Guarani, Catalan and Basque, is common.
At present, the distinction between y and ll remains in Colombia in a zone around Bogotá and Popayán, the southern Ecuadoran highlands, Andean and south coastal Peru, most of Bolivia and Paraguay, San Juan and La Rioja provinces in Argentina, as well as the regions bordering Paraguay, and in isolated pockets in the south of Chile. The distinction is more common in areas where bilingualism with indigenous languages such as Aymara and Guaraní is common. In Spain, most of the northern half of the country and several areas in the south used to retain the distinction, but urban areas have seen yeísmo spreading very quickly, and the distinction is now lost in most of Spain (see External links).
Minimal pairs 
- haya ("beech tree" / "that there be") ~ halla ("s/he finds")
- cayó ("s/he fell") ~ calló ("s/he became silent")
- hoya ("pit, hole") ~ olla ("pot")
- baya ("berry") / vaya ("that he go") ~ valla ("fence")
Due to the relatively low frequency of both /ʝ/ and /ʎ/, confusion is unlikely. However, orthographic mistakes are common (for example, writing llendo instead of yendo). A similar effect took place in the local name of the island of Majorca: Mallorca is a continental Catalan hypercorrection of the earlier Maiorca.
- "La "i griega" se llamará "ye"" Cuba Debate. 2010-11-05. Retrieved 25 November 2010.
- Alfredo Ignacio Álvarez, Hablar en español: la cortesía verbal, la pronunciación estándar del español, las formas de expresión oral (2005), Universidad de Oviedo, p. 104.
- Schwegler, Kempff and Ameal-Guerra, Fonética y fonología españolas (2009), John Wiley & Sons, p. 399.
- Catherine E. Travis, Introducción a la lingüística hispánica (2009), Cambridge University Press, p. 76.
- Lapesa, Rafael. "El español de América" (in Spanish). Cultural Antonio de Nebrija.
- Diccionari català-valencià-balear, Institut d'Estudis Catalans (look up the term "Mallorca")
Torreblanca, Máximo (1974), "Estado actual del lleísmo y de la h aspirada en el noroeste de la provincia de Toledo", Revista de dialectología y tradiciones populares 30 (1-2): 77–90