There are 5 letters for vowels (a, e, i, o, u) and 20 for consonants. The letters q, w, x, y are excluded from the standard spelling, as are some Serbo-Croatian graphemes ( ć, đ), however they are collated as independent letters in some encyclopedias and dictionary listings; foreign proper nouns or toponyms are often not adapted to Slovene orthography as they are in some other Slavic languages, such as partly in Russian or entirely in the Serbian standard of Serbo-Croatian.