Tertiary source

A tertiary source is a compilation or index of previously published primary and secondary sources, offering no new interpretation or analysis. It can help locate seminal works, key terms, general knowledge, and established scientific consensus on a subject. The precise meaning of "tertiary" depends on the academic discipline.

In academic research, tertiary sources like encyclopedias are generally not accepted as citations, though survey articles are often cited instead of the original publication.

The line between secondary and tertiary sources is not always clear, much like the distinction between primary and secondary sources in some fields. Depending on the research topic, a scholar might treat a bibliography, dictionary, or encyclopedia as either secondary or tertiary. This makes it difficult to definitively classify many sources. In some disciplines, the difference is relative. Under the UNISIST model, a secondary source is a bibliography, while a tertiary source is a synthesis of primary sources.

Tertiary sources may be in book form, often organized alphabetically, or online, where they are searchable by keyword. Examples include reference books, encyclopedias, dictionaries, some textbooks, abstracts, directories, factbooks, handbooks, manuals, and compendia. Indexes, bibliographies, concordances, and databases aggregate primary and secondary sources and are often considered tertiary; they may also provide access to full or partial texts of those sources. Almanacs, travel guides, field guides, and timelines are further examples. Tertiary sources aim to summarize, collect, and consolidate material into an overview without adding new analysis or conclusions. Wikipedia is a tertiary source.