Question

Define "data definition language"?

Answer 1

Data definition language (DDL) is a standard for command that define different structures in a database.

Answer 2

Data Definition Language (DDL) [ also known as Data Description Language as it describes fields and records in database table]* is typically a subset computer language of SQL (Structured Query Language )  use to create and modify the structure of database objects.
Database industry incorporates DDL into any formal language describing data.
So, DDL doesn't show up as a different language in SQL but does define self in a database.