Is it ensure, insure, or assure?
Roman freedman who became a learned scholar and grammarian and the most famous teacher of his day. Verrius Flaccus introduced the principle of competition among his pupils and awarded old books, beautiful or rare, as prizes. Augustus entrusted the education of his two grandsons to him, and thenceforward his school was in the imperial house on the Palatine. He died at an advanced age during the reign of Tiberius.