is a phenomenon in Spanish grammar, considered "wrong" in prescriptive works. It is the practice of using instead of as the complementizer introducing a verbal complement clause. It can be seen as the opposite of , which involves using when is to be used.
For example, ("He told me that he was tired"), is a case of since the prescriptive construction is . is considered peculiar to less educated speakers, most likely as an instance of hypercorrection in the attempt to avoid or perhaps a conflation with the reflexive use, which can sometimes be quite superficially similar:
(Grammatically normal, with a reflexive verb: "I am pleased...") (Prescriptively incorrect, non-reflexive , usually "It pleases me...")
References
Bentivoglio, Paola. 1975. "" In Frances M. Aid, Melvyn C. Resnick, and Bohdan Saciuk (eds.), Colloquium on Hispanic Linguistics (Washington: Georgetown University Press), pp. 1–18. . Carbonero, Pedro. 1992. "" In Elizabeth Luna Traill (ed.), (Mexico City: ), pp. II: 43-63. Gomez Torrego, Leonardo. 1991. "" , 55: 23-44. McLauchlan, Jessica, 1982. "" , 6 (1): 11-55. Rabanales, Ambrosio. 1974. "" In María Josefina Tejera (ed.), (Caracas: ), pp. 413–444. Also in Juan M. Lope Blanch (ed.), (Mexico City: , 1977), pp. 541–569.