The article: ὁ, ἡ, τότὸ ἄρθρον

ὁ, ἡ, τό means "the". It is the commonest word in Greek, and it is your best friend: it usually agrees with its noun, so the article tells you the noun's gender, number and case even before you know the noun.

Greek nouns have three genders: masculine, feminine and neuter. Gender is grammatical: λόγος "word" is masculine, ψυχή "soul" feminine, δῶρον "gift" neuter. Learn each noun with its article: ὁ λόγος, ἡ ψυχή, τὸ δῶρον.

There are four cases to learn now. Besides the nominative (subject) and accusative (object): the genitive is roughly English of ("the word of the god"), and the dative roughly to or for ("he gave it to the man").