Learn Italian: Il problema è essenzialmente economico. - The problem is essentially economic.

The adverb comes from the adjective essenziale. Normally, to form an adverb, you add -mente to the feminine singular form of the adjective. However, when an adjective ends in -le or -re (like essenziale, facile, or particolare), you drop the final e before adding -mente to make pronunciation smoother.

Why does the adjective economico end in -o when the noun it modifies, problema, ends in -a?

Problema is masculine, despite ending in -a. This is a common pattern for Italian words of Greek origin ending in -ma (like il sistema or il programma). Because il problema is masculine singular, the adjective describing it must also take the masculine singular ending, resulting in economico.

Could I use fondamentalmente instead of essenzialmente in this sentence?

Yes, they are highly interchangeable here. Both mean essentially or fundamentally. Essenzialmente highlights the core nature (the essence) of the issue, while fondamentalmente points to the root foundation, but in everyday conversation, Italians use either one to express the exact same idea.

Why does the adverb sit between the verb and the adjective?