Slovak is the official language. It belongs to the western Slavic group and is written in the Roman alphabet. There are only slight differences between Slovak and Czech, and the two are mutually intelligible. Slovak lacks the e, u˚, and r in Czech but adds ä, l', ô, and ŕ. As in Czech, q, w, and x are found only in foreign words. A minority language like Hungarian may be used for official business if its speakers make up at least 20% of the population on the local level.