diurnum

Substantivization of diurnus (“day”, relational adjective). Sense 3 documented from the fourth century AD.^[1]

• (Classical Latin) IPA^(key): [diˈʊr.nũː]
• (modern Italianate Ecclesiastical) IPA^(key): [d̪iˈur.num]

diurnum n (genitive diurnī); second declension

1. a day's ration, daily proportion or allowance
2. an account book of day-to-day issues, daybook, record, minutes
   • 121 C.E., Suetonius, De Vita Caesarum:

     Extat talis scriptura in plerisque libris ac diurnis titulisque operum.

     We can still to this day see this font in number of books, account books, and on the front of many buildings.

3. (Late Latin) day (specifically the time when the sun is up)

   Synonym: diēs

Second-declension noun (neuter).

diurnum

1. inflection of diurnus:
   1. masculine accusative singular
   2. neuter nominative/accusative/vocative singular

• "diurnum", in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• diurnum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
• “diurnum”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press