• lēthālis

From lētum (“death; ruin”) +‎ -ālis.

• (Classical Latin) IPA^(key): [ɫeːˈtaː.lɪs]
• (modern Italianate Ecclesiastical) IPA^(key): [leˈtaː.lis]

lētālis (neuter lētāle); third-declension two-termination adjective

1. lethal, deadly, fatal, mortal

   Synonyms: capitālis, pestifer

   • c. 1129, Henricus Huntindoniensis, edited by Thomas Arnold, Historia Anglorum‎^[1], published 1879, page 194:

     Quem cum bello caesum patri renuntiassent, ait: "Recepitne vulnus letale in anteriori vel posteriori corporis parte?" Dixerunt nuntii: "In anteriori."

     And when they had reported his death during the battle to his father, he said: "Did he receive the lethal blow on the front or the back of his body?" The messengers said: "In the front."

   • 2007, Carolus Petreius Bogotensis, Niponum gallinae probantur viru aviarii morbi contactae‎^[2], Ephemeris:

     Biologici Nipones affirmant virus H5N1 {...} esse letale.

     Japanese biologists confirm that the H5N1 virus {...} is lethal.

Third-declension two-termination adjective.

• lētifer
• lētō
• lētum

• “letalis”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• “letalis”, in Charlton T. Lewis (1891), An Elementary Latin Dictionary, New York: Harper & Brothers
• “letalis”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.