Yeísmo (pronounced /ʝeˈizmo/) 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 /ɟʝ/ (written y), usually realized as a palatal fricative or affricate. The term yeísmo comes from the Spanish name of the letter y (i griega or ye). The opposite phenomenon, lleísmo (pronounced /ʎeˈizmo/), is the realization of both as the palatal lateral approximant phoneme /ʎ/.
Most dialects currently realize the merged phoneme as a voiced palatal fricative [ʝ], which becomes an affricate or a plosive (either a voiced postalveolar affricate [ʤ] as in English gin, a voiced palatal affricate [ɟ͠ʝ] when it occurs after a pause (as at the beginning of a sentence) or after a nasal (as in the words cónyuge and conllevar). However, in Rioplatense it is typically realized as a voiced postalveolar fricative [ʒ], called zheísmo (or as a voiceless postalveolar fricative [ʃ], called sheísmo, among the younger generations), which may become a voiced postalveolar affricate [ʤ] (or voiceless postalveolar affricate [ʧ] among the younger) in the same context as above.
Due to the relatively low frequency of both y and ll, confusion is unlikely. However, orthographic mistakes are common (for example, writing llendo instead of yendo — for some reason, most people tend to err towards ll). A similar effect took place in the local name of the island of Majorca: Mallorca is a continental Catalan hypercorrection of the earlier Maiorca.