Adjective

An adjective modifies (gives more information) about another word. In greek, an adjective can function in three ways"
 * attributive - it gives an attribute or description about something, usually a noun or pronoun. E.g. The good man....
 * predicate - it states a fact about something, usually a noun or pronoun. E.g. The man is good.
 * substantival - it stands in the place of a noun. E.g. You can have the large or the small....

An adjective agrees with the word it modifies in case, gender and number. That is why a typical dictionary entry for an adjective will list it in all three genders.

The article can be helpful in seeing what the adjective is doing in a sentence.

Attributive

 * In attributive usage, an adjective must agree the word it modifies in case, gender, number.
 * There are two patterns:
 * 1st attributive positon - ὁ ἀγαθὸς ἄνθρωπος (the good man - like in English)
 * 2nd attributive position - ὁ ἄνθρωπος ὁ ἀγαθός (the man the good. Note the article must precede both noun and adjective)