merriam-webster.com

Definition of IDEM

: the same as something previously mentioned —used chiefly in bibliographies

Word History

Etymology

Middle English, from Latin, same — more at identity

First Known Use

before the 12th century, in the meaning defined above

Time Traveler

The first known use of idem was before the 12th century

“Idem.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/idem. Accessed 4 Mar. 2025.

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!