What is the meaning of -ий?

Marks the genitive case in the regular declension after a front vowel stem ending in н (n).

Forms patronymics.

forms relational and possessive adjectives from nouns describing animals and people: -'s, -ine, -ian

-ed

forms adjectives from verbs, verbal nouns and compounds: -ous, -al, etc.

forms adjectives and adjectival nouns from some nouns referring to people

forms names of chemical elements, especially metallic ones: -ium

Cyrillic spelling of -iy

Source: wiktionary.org