(a) Agency – the principal administrative organization of state government as defined in Section 25-9-107(d), headed by an executive director or such other official as prescribed by statute;
(b) Office – the principal organization of an agency; whenever the term “division” or any other term appears to denote the principal organization of a department, it shall mean “office” for purposes of this section;
(c) Bureau – the principal organization of an office;
(d) Division – the principal organization of a bureau;
(e) Branch – the principal organization of a division;
(f) Section – the principal organization of a branch;
(g) Unit – the principal organization of a section;
(h) Advisory board – a body appointed to function on a continuing basis to study and recommend solutions and policy alternatives to problems arising in a specific agency or program of state government.