The term 'that is to say' is used to introduce an explanation or clarification of a statement. It can be expressed in various ways, such as 'NAMELY' (6 letters), 'VIDELICET' (9 letters), 'VIZ' (3 letters), 'idest' (5 letters), 'imean' (5 letters), 'towit' (5 letters), and 'imeant' (6 letters). All of these words are synonyms for the phrase 'that is to say' and are used to provide further information about a statement.