5.1.2. Number of Italian nouns and noun-ending changes
Singular and plural of nouns, singolare e plurale dei nomi
Masculine nounds ending in –o in the singular usually change to –i in the plural, e.g., i quaderni. Feminine nouns ending in –a in the singular usually change to –e in the plural, e.g., le piante.
Regardless of its gender, a noun that ends in –e in the singular will usually change to –i in the plural. E.g., i giornali, le chiavi.