Librettos
Plural form of Libretto is Libretti.
I don't know I'm so sorry!
Libretto is the singular. Libretti is the plural. Sometimes librettos is also commonly used as the plural.
librettos
Forum---Plural Form Forums,Foreign Plural Form Forumina
Liberetti
The plural form of apparatus is apparatuses. It has no foreign plural.
The foreign plural form of symposium is symposia, while the English plural form is symposiums.
data IS the plural form of datum.
Ova is the plural form. The singular form is ovum.
octopi
The plural form of the noun 'bandit' is bandits.The noun 'bandits' is a 'regular plural' form, a word that forms its plural by adding an 's' or an 'es' to the end of the word.