凱爾特語系 refers to a branch of the larger 印歐語系, which includes languages historically spoken by the 凱爾特人. This language family is primarily divided into two groups: 古凱爾特語 and 現代凱爾特語. The modern languages include 愛爾蘭語, 威爾士語, 布列塔尼語, and 蘇格蘭蓋爾語. The 凱爾特語系 is notable for its rich cultural heritage and historical significance in regions such as 愛爾蘭, 威爾士, and 蘇格蘭. These languages are not only important for communication but also play a crucial role in preserving the traditions and identities of the 凱爾特 peoples.