A more thorough explanation:

Definition: Justinian's Institutes is an elementary treatise on Roman law in four books. It is one of the four component parts of the Corpus Juris Civilis.

Examples:

• Coke's Institutes in four volumes (published in 1628) is a legal treatise or commentary.
• Gaius wrote an elementary treatise on Roman law in the second century A.D., which served as a foundation for Justinian's Institutes.
• Theophilus, a law professor at Constantinople, wrote a paraphrase of Justinian's Institutes in Greek in the sixth century A.D.

The examples illustrate the different types of institutes, including legal treatises or commentaries, elementary treatises on Roman law, and paraphrases of Justinian's Institutes. These institutes are important resources for studying and understanding Roman law.