COMMENTARII, notes to assist the memory, memoranda. This original idea of the word gave rise to a variety of meanings: notes and abstracts of speeches for the assistance of orators; family memorials, the origin of many of the legends introduced into early Roman history from a desire to glorify a particular family; diaries of events occurring in their own circle kept by private individuals—the daybook, drawn up for Trimalchio in Petronius (Satyricon, 53) by his actuaries (a slave to whom the duty was specially assigned) is quoted as an example; memoirs of events in which they had taken part drawn up by public men— such were the "Commentaries" of Caesar on the Gallic and Civil wars, and of Cicero on his consulship. Different departments of the imperial administration and certain high functionaries kept records, which were under the charge of an official known as a commentariis (cf. a secretis, ab epistulis).
The Commentarii Principis were the register of the official acts of the emperor. These must be distinguished from the com mentarii diurni, a daily court-journal. At a later period records called ephemerides were kept by order of the emperor ; these were much used by the Scriptores Historiae Augustae (see AUGUSTAN HISTORY). The Commentarii Senatus, only once mentioned (Tacitus, Annals, xv. 74) are probably identical with the Acta Senatus (q.v.). There were also Commentarii of the priestly colleges. Mention should be made of the Commentarii Regum, containing decrees concerning the functions and privileges of the kings, and forming a record of the acts of the king in his capacity of priest.
See the exhaustive article by A. von Premerstein in Pauly-Wissowa, Realencyklopddie ('9oi) ; Teuffel-Schwabe, Hist. of Roman Lit. (Eng. trans.), pp. 72, 77-79; and the concise account by H. Thedenat in Daremberg and Saglio, Dictionnaire des antiquites.