Md. Code, General Provisions § 1–105

In this Code, a code of public local laws, a municipal charter, a resolution or ordinance of a county or municipal corporation, or a rule, regulation, or directive of a unit of the State or a political subdivision of the State:

(1) “certified mail” and “registered mail” include the uses, procedures, and fees of the United States Postal Service;

(2) “certified mail” includes “registered mail”; and

(3) “registered mail” includes “certified mail”.