Series

• Record Group
• Collection
• Series
• Creator
• File Unit
• Item

Series

File units or items arranged in accordance with a filing system or maintained as a unit because they result from the same accumulation or filing process, the same function, or the same activity; have a particular form; or because of some other relationship arising out of their creation, receipt, or use.

For example the series "Civil Case Files, 1936 – 1980" consists all of the civil cases filed in the U.S. District Court for the Nashville Division of the Middle District of Tennessee and is part of Record Group 21, Records of District Courts of the United States.