Bilingual inscription
In epigraphy, a bilingual is an inscription that is extant in two languages (or trilingual in the case of three languages, etc.). Bilinguals are important for the decipherment of ancient writing systems, and for the study of ancient languages with small or repetitive corpora.
Important bilinguals include:
the Rosetta Stone, in hieroglyphic and demotic Egyptian and Greek
the Behistun Inscription, in Old Persian, Elamite, and Babylonian (a later form of Akkadian)
the Armazi stele of Serapit, in Ancient Greek and Aramaic
the Cippi of Melqart, in Ancient Greek and Carthaginian discovered in Malta in 1694, the key which allowed French scholar Abbé Barthelemy to decipher Phoenician
the Xanthos Obelisk
the Letoon trilingual, in standard Lycian or Lycian A, Greek and Aramaic
the Karatepe inscriptions, in Phoenician and Hieroglyphic Luwian
the Amathus Bilingual, in Eteocypriot and Greek
the Pyrgi Tablets, in Etruscan and Phoenician
the Kaunos Bilingual, in Carian and Greek
the bilingual Punic-Libyan Inscription from the Mausoleum of Ateban, Dougga, now held at the British Museum