source codes:

[AAT]

Art & Architecture Thesaurus

[TGN]

Thesaurus of Geographic Names

[ULAN]

Union List of Artist Names

Library of Congress:

[LCNAF]

Name authority

[LCSH]

Subject headings

[LCTGM]

Graphic materials

[ICONCLASS]

Definition:

Terms or phrases that describe, identify, or interpret the Work or Image and what it depicts or expresses. These may include generic terms that describe the work and the elements that it comprises, terms that identify particular people, geographic places, narrative and iconographic themes, or terms that refer to broader concepts or interpretations.

Wikicatalog Use:

Repeat additional subjects under existing entries. Follow entry with source code e.g. [AAT]. 

Data Values: AAT, TGN, LCTGM, ICONCLASS, LCSH, LCNAF

VRA Core 4: <subject>

CCO: Part TWO: Chapter 6: Subject

CDWA: Subject Matter

Dublin Core: Subject

Examples:

landscapes (representations) [AAT]

Venus (Roman deity) [LCSH]

Jesus Christ -- Crucifiction [LCSH]

Labor movement -- England -- 19th century [LCSH]