The different pattern that applies for various nouns and adjectives in Greek regarding the morphological changes they go through in the various cases, in singular and plural and in the three genders (masculine, feminine and neuter). E.g. the word λίμνη belongs in the first declension group (η λίμνη, της λίμνης κλπ.), while the word άνθρωπος in the second one (ο άνθρωπος, του ανθρώπου κλπ.).

It is the system according to which the various categories of nouns (masculine, feminine or neuter) change their endings in the singular and the plural and in their cases. E.g. the garden – the gardens.

The parts of speech that are conjugated, i.e. change morphologically depending on the case, number and gender. The declinable parts of speech in Greek are articles, nouns, adjectives, pronouns, verbs and participles.