The Institutes of Justinian (Latin: Institutiones Justiniani) is a unit of the Corpus Juris Civilis, the sixth-century codification of Roman law ordered by the Byzantine emperor Justinian I. It is largely based upon the Institutes of Gaius, a Roman jurist of the second century A.D. The other units in the Corpus Juris Civilis are the Digest, the Codex Justinianus, and the Novellae Constitutiones ("New Constitutions" or "Novels").[1]