List of ambassadors of the United States to Sierra Leone

Career FSO
After 1915, The United States Department of State began classifying ambassadors as career Foreign Service Officers (FSOs) for those who have served in the Foreign Service for a specified amount of time.

Political appointee
A person who is not a career foreign service officer, but is appointed by the president (often as a reward to political friends).

Appointed
The date that the ambassador took the oath of office; also known as “commissioning”. It follows confirmation of a presidential appointment by the Senate, or a Congressional recess appointment by the president. In the case of a recess appointment, the ambassador requires subsequent confirmation by the Senate to remain in office.

Presented credentials
The date that the ambassador presented his letter of credence to the head of state or appropriate authority of the receiving nation. At this time the ambassador officially becomes the representative of his country. This would normally occur a short time after the ambassador’s arrival on station. The host nation may reject the ambassador by not receiving the ambassador’s letter, but this occurs only rarely.

Terminated mission
Usually the date that the ambassador left the country. In some cases a letter of recall is presented, ending the ambassador’s commission, either as a means of diplomatic protest or because the diplomat is being reassigned elsewhere and replaced by another envoy.

Chargé d'affaires
The person in charge of the business of the embassy when there is no ambassador commissioned to the host country.

Ad interim
Latin phrase meaning "for the time being", "in the meantime".