Fromdēsignō(“designate, describe”) +‎-tiō.

• (Classical Latin)IPA^(key):/deː.siɡˈnaː.ti.oː/,[d̪eːsɪŋˈnäːt̪ioː]
• (modern Italianate Ecclesiastical)IPA^(key):/de.siɲˈɲat.t͡si.o/,[d̪es̬iɲˈɲät̪ː͡s̪io]

dēsignātiō f (genitivedēsignātiōnis);third declension

1. adesignating,describing,marking out,specification
2. adisposition,arrangement

Third-declension noun.

• dēsignātē
• dēsignātor
• dēsignātus
• dēsignō
• signō

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