Definition
Latin: "in the meantime." Ad interim denotes a temporary, provisional, or interim capacity — most commonly applied to appointments, arrangements, or authorizations that fill a gap until a permanent arrangement is established. An officer appointed ad interim holds office temporarily, either to fill a vacancy or to perform the duties of a regular incumbent during that person's absence or incapacity. The designation signals that the appointment is not permanent and carries no implication that the interim holder has a claim to the permanent position.
Common Language
Modern common usage (Wiktionary): "In or for the meantime; temporarily."
Historical common usage (Webster's 1913): "Meanwhile; temporary."
The common and legal meanings are close, but the legal use carries structural significance that ordinary usage does not. In legal and governmental contexts, ad interim is not merely descriptive of a time period — it defines the legal authority and limits of a position or arrangement. An ad interim appointment may trigger specific procedural requirements, limit the powers available to the holder, or require subsequent ratification to become permanent.
Why It Matters in Research
Researchers encounter ad interim most frequently in three contexts: government appointment records, corporate governance documents, and international legal instruments.
In public law sources, ad interim appointments have generated recurring questions about whether interim officers exercise the full statutory powers of the permanent position. Historical administrative records, executive orders, and agency documents often use ad interim interchangeably with "acting" — but these are not always legal equivalents. A researcher treating them as synonyms in modern administrative law sources risks error; the distinction between an "acting" officer and an officer formally designated ad interim has mattered in challenges to agency authority.
In diplomatic and treaty sources, ad interim appears frequently as a title — Chargé d'Affaires ad interim, for example — denoting a diplomat temporarily heading a mission in the absence of the principal. These usages follow international convention and carry specific protocol and legal consequences under the Vienna Convention on Diplomatic Relations.
In corporate records, resolutions appointing an officer ad interim signal a board's intent to make only a provisional appointment, which may affect the officer's contracting authority depending on the jurisdiction and the company's governing documents.
Historical corpus sources using ad interim may reflect older appointment practices and statutory frameworks that differ significantly from modern ones. Treat the term as a flag to investigate the specific authority structure, not as a self-explanatory descriptor.
Historical Dictionary Support
Both the first and second editions of Black's Law Dictionary give identical definitions: "In the mean time," followed by the officer-appointment illustration. The entry is stable across editions, which reflects the term's fixed Latin meaning rather than any legal evolution. Neither edition addresses the distinction between ad interim and "acting" as a matter of legal authority — an omission that matters for modern research. The historical dictionaries also do not address the international diplomatic usage or corporate contexts. For those applications, researchers must go beyond the dictionary shelf to treatises, statutes, and applicable conventions.
Jurisdictional Note
In U.S. federal law, the distinction between an "acting" officer and an ad interim designee has constitutional and statutory dimensions governed by the Vacancies Reform Act and related doctrine. State law varies considerably in how it regulates interim appointments and whether interim officers exercise full or restricted authority. Researchers should not assume uniform treatment across jurisdictions.
Encyclopedia Cross-Reference
No Law Mind Encyclopedia entry directly addresses ad interim appointments as a standalone topic. For the guardian ad litem usage — a distinct Latin appointment concept sharing the "ad" construction — see: Child Custody — Custody Evaluations and Guardian ad Litem (The Law Mind Family Law Encyclopedia).