You will often hear or see the term RDBMS or Relational Database Management System. This term refers to a subset of DBMS, not an alternative, and is specific to those DBMS that handle relational database formats. The term SQL is often incorrectly applied to these, but SQL is a language and relational databases are a mathematical model. While the two have a relationship (no pun intended) they are different things completely and are not directly tied together. Today, what is and is not an RDBMS is increasingly unclear as nearly all DBMS have some relational element and even the most traditional RDBMS stalwarts have begun to add non-relational engines or options.