Learn Italian: La profondità massima del cratere è un problema minore. - The maximum depth of the crater is a minor problem.

massima is the feminine singular form of the irregular superlative massimo (greatest or maximum). It has to match the noun it describes, profondità, which is feminine because nouns ending in -tà are almost always feminine in Italian.

Why do we use minore here instead of minimo?

minore is the irregular comparative for piccolo (small), meaning lesser or minor. minimo is the absolute superlative, meaning least or minimum. Since the sentence talks about a minor problem rather than the absolute smallest problem, we use minore.

problema ends in -a, so why does it use the masculine article un?

problema is a common exception to the usual gender rules. It comes from Greek, and in Italian, many Greek root words ending in -ma (like il sistema or il clima) are masculine. Therefore, it takes the masculine article un.

Why do massima and minore come after their nouns here?

In Italian, adjectives generally follow the noun when they classify it or add a defining fact. Here, massima specifies the exact type of depth, and minore classifies the category of the problem, so they naturally follow the noun.