What are stem-changing verbs in Spanish

Los verbos con cambio de raíz de O a UE: lista y oraciones

Los cambios de raíz en español son necesarios para cambiar la ortografía del verbo para mantener una pronunciación similar del verbo en infinitivo una vez que dicho verbo se ha conjugado.

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21. both telenovelas and soap operas are serial melodramatic genres in contrast, it's a rare event that a soap opera actor transitions well to into hollywood.22. the san sebastian international film festival- it is the only film festival in spain listed as a category “a” event, one of only 13 in the whole world.  the malaga film festival- the official name of the event is festival de málaga cine español (fmce) and began in 1998 to drive the spanish film industry.23. there are two main reasons for regional television in spain. the first is so that people can get the news in a timely fashion, the other is for entertainment.  24.the goya awards are just like the oscar basically. the goya awards are for the best spanish films of the years.25.she was the first woman to receive a chair at a spanish university and her home in la coruña, which belongs to the real academia galega, now houses the casa-museo pardo bazán, dedicated to the conservation and dissemination of the author's heritage