From Wikipedia:

Frisian language can refer to:

The Frisian languages, a closely related group of three Germanic languages:

o West Frisian language (fy), spoken in the Netherlands and often known there simply as the Frisian language

o Saterland Frisian (frs) or East Frisian language, spoken in Lower Saxony, Germany

o North Frisian language (frr), spoken in Schleswig-Holstein, Germany

o East Frisian Low Saxon, the West Low German dialect of East Frisia, Lower Saxony, Germany

Wikipedia: Frisian languages (English)
Wikipedia: Friesische Sprache (German)
Wikipedia: Fryske talen (Frisian)