Learn Italian: La sua debolezza è il cioccolato.

The noun debolezza (weakness) is formed by taking the root of the adjective debole (weak) and adding the suffix -ezza. This suffix works just like the English suffix -ness to create abstract nouns representing a state or quality.

Are nouns ending in the suffix -ezza always feminine?

Yes! Abstract nouns created with the -ezza suffix are always feminine. Because of this rule, the sentence must use the feminine article la and the feminine possessive adjective sua.

Wait, if the noun is feminine, how do we know it means his weakness and not her weakness?

We can only tell from the broader conversation. In Italian, the possessive adjective sua agrees with the gender of the thing being possessed (debolezza, which is feminine), not the gender of the owner. Therefore, La sua debolezza could translate to his weakness, her weakness, or even the formal your weakness.

Why do we need the article il before cioccolato if the English translation just says chocolate?

In Italian, definite articles like il or la are required when you talk about a general category, substance, or broad concept. Because the sentence refers to chocolate in general as a weakness, rather than a specific piece of chocolate, you must include il.