Silesian language can refer to the Silesian - a dialect of Polish, sometimes considered a separate Western Slavonic language related to Czech and Polish), or the Lower Silesian (a dialect of German). Both are spoken in the region of Silesia.
Majority of Slavic linguists consider it as a dialect of Polish, however some people regard it as a separate language belonging to the West Slavic branch of Slavic languages, together with Polish, Upper and Lower Sorbian, and other Lekhitic languages) as well as Czech and Slovak.
According to the last census in Poland (2002) some 70,000 people declared Silesian as their first language, and some 170,000 people declared Silesian nationality.
While mutual intelligibility is not the sole determinant of when a spoken dialect becomes a separate language, Silesian is not mutually intelligible with Polish. Polish speakers can understand majority of words, though. The issue of whether Silesian is a dialect or a language can be contentious since some Silesians consider themselves to be a distinct ethnic minority or nationality within Poland and some people disagree with this.
When classified as a dialect, it is the most prominent regional dialect of the Polish language which is classified in the West Slavic branch of Slavic languages.
When classified as a language, it is considered closely related to Polish and then Czech with some influence from German.
Silesian is spoken in the region of Silesia in south-western Poland and north-eastern Czech Republic and in a couple of place all around the world.
At present the Silesian is commonly spoken in the area between historical border of Silesia on the east, and line Sycow - Prudnik on the west.