Functions of Cases (so far)

The subject of the sentence. (Ex. The son knows God. -- ο υιος γινωσκει τον θεον)

The predicate, i.e. a noun that modifies the subject. Often appears to complete the clause with the verb "to be" or similar verbs. (Ex. The son is a human being. -- ο υιος εστι ανθρωπος) To determine which of the two nominative nouns is the subject, one can use the following rule: if both nouns simultaneously have an article or simultaneously lack one, then the one that appears first is the subject; if one noun has an article and another does not, then the noun with the article is the subject.

Possessive form. Expresses possession, belonging, or origin. In most cases, can be translated to English using the preposition of. Always modifies another noun. Appears either after the noun it modifies or between the noun and the article. (Ex. The son of God. -- ο υιος του θεου or ο του θεου υιος)

An object of a prepositional phrase with the preposition that governs the Genitive.

The indirect object of a verb. More generally: the recipient, the purpose, or the goal of an action. Can be translated as an indirect object or using prepositions to or for. (Ex. God sent men the son. -- ο θεος πεμπει ανθρωποις ο υιος)

The dative of means: the object or a circumstance that enables the action or with which the action is performed. Can usually be translated using prepositions by or with. (Ex. The man kills the son with a sword -- ο ανθρωπος αποκτεινει τον υιον τη μαχαιρα)

An object of a prepositional phrase with the preposition that governs the Dative.

The direct object of a verb. (Ex. The son knows God. -- ο υιος γινωσκει τον θεον)

An object of a prepositional phrase with the preposition that governs the Accusative.