Greek Definite Article

The definite article is employed in combination with nouns, and is declined in gender, number, and case, to correspond with them. The Greek article is the same form as the demonstrative ο, η, το. The Greek article must be in the gender, number and case of the noun to which it belongs, according to the rule. “Adjectives, participles, and pronouns must agree with their substantives in gender, number and case.” (Second concord)

The article is often found with abstract nouns when regarded as separate objects of thought.

There is no indefinite article in Greek, but its place is often supplied by the indefinite pronoun (any, a certain).