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Italian was a language spoken on the planet Earth, originating from Latin in the nation-state of Italy.

When Sybok the God of Sha Ka Ree he inquired "Qual sei tu", which mean "Who art thou" in Italian. (Star Trek V: The Final Frontier)

Leonardo da Vinci in the holodeck program created by Kathryn Janeway, as well as various others, occasionally spoke Italian:

Italian term/phase	English translation	Reference
Amici	Friends	VOY: "Concerning Flight"
Andiamo!	We go!	VOY: "Scorpion"
Benissimo	Very well	VOY: "Concerning Flight"
Buon giorno	Good day	VOY: "Concerning Flight"
Buffo	Funny	VOY: "Concerning Flight"
Buona sera	Good evening	VOY: "Scorpion"
Che bella!	That beauty!	VOY: "Scorpion"
Che cazzo!	That fuck!	VOY: "Scorpion"
Che meraviglia!	That wonder!	VOY: "Concerning Flight"
Esatto	Exactly	VOY: "Scorpion", "Concerning Flight"
Finito	Finished	VOY: "Concerning Flight"
Grazie	Thank you	VOY: "Concerning Flight"
Madonna mia!	My Lady!	VOY: "Concerning Flight"
Maestro	Teacher/Master	VOY: "Scorpion", "The Raven", "Concerning Flight", "Someone to Watch Over Me", "Virtuoso"; ENT: "Babel"
Meraviglioso!	Marvelous!	VOY: "Scorpion"
Momento	Moment	VOY: "Concerning Flight"
Scusi	Excuses	VOY: "Scorpion", "Concerning Flight"
Signorina	Miss	VOY: "Scorpion", "Concerning Flight"
Signore/Plural: signori	Gentleman	VOY: "Concerning Flight"
Stupido animale	Stupid animal	VOY: "Concerning Flight"
Terremoto	Earth movement	VOY: "Concerning Flight"

Background Edit

The Star Trek: Voyager episode title "Virtuoso" is Italian, meaning virtuous or master.