The Roman jurist Gaius wrote a textbook for first-year law students around 161 AD. The four books of his 'Institutiones' are the only nearly complete surviving textbook of Roman civil law from antiquity. The work is preserved in a single manuscript, produced around 500 AD, which is very difficult to read. The discovery of this manuscript has significantly expanded our knowledge of Roman law. The Latin text printed here is based on the evaluation of 19th-century copies and modern critical editions; any unreadable and therefore presumed or supplemented letters are indicated in italics. For larger text passages that could not be read in the manuscript, the editor suggests possible supplements. Latin technical terms are...