Learn Italian: Napoli è la città più economica del sud. - Naples is the cheapest city in the south.

In Italian, descriptive adjectives usually come after the noun. To form a relative superlative, you use the definite article, then the noun, then più or meno, and finally the adjective. This is why la città più economica literally flows as the city most cheap.

Why does the sentence use del sud instead of nel sud for in the south?

When you state the group or place in a superlative comparison, English uses in, but Italian requires the preposition di. Since sud uses the masculine article il, the preposition di merges with it to become the articulated preposition del.

Why does the adjective economica end in an a?

Adjectives must match the gender and number of the noun they describe. Because città is a feminine singular noun, the dictionary form of the adjective, economico, changes its ending to match, becoming economica.

The word città has an accent at the end. Does that change how it works in a sentence?