A more thorough explanation:

Definition: Registrum originale (ri-jis-trum -rij--nay-lee) is a Latin term used in history to refer to the register of original writs. It is abbreviated as reg. orig.

Example: The Registrum originale contains the original writs issued by the English Chancery from the 13th to the 19th century.

Explanation: The example illustrates how the Registrum originale is a collection of original writs issued by the English Chancery over a period of six centuries. These writs were recorded in the register to keep a record of the legal proceedings and to ensure that they were conducted according to the law.