OriginFeminine plural nominative & accusative, masculine plural accusative forms of annar.
Formsannar(masculine, nominative, singular) · onnur(feminine, nominative, singular) · annað(neuter, nominative, singular) · annan(accusative, masculine, singular) · aðra (aðru)(accusative, feminine, singular) · annað(accusative, neuter, singular) · øðrum(dative, masculine, singular) · aðrari (aðru)(dative, feminine, singular) · øðrum(dative, neuter, singular) · annars(genitive, masculine, singular) · annarar(feminine, genitive, singular) · annars(genitive, neuter, singular) · aðrir(masculine, nominative, plural) · aðrar(feminine, nominative, plural) · onnur(neuter, nominative, plural) · aðrar(accusative, masculine, plural) · aðrar(accusative, feminine, plural) · onnur(accusative, neuter, plural) · øðrum(dative, plural) · annara(genitive, plural)
Source: Wiktionary