Synonymy occurs when a concept can be represented by multiple terms having the same or similar meanings. The desired content may be difficult to retrieve because it can be described by different but equivalent terminology.

Words: Artificial consciousness, Biocomputers, Electronic brains, Mechanical brains, Synthetic consciousness, Concept: Conscious automata

A controlled vocabulary must compensate for the problems caused by synonymy by ensuring that each concept is represented by a single preferred term. The vocabulary should list the other synonyms and variants as non-preferred terms with USE references to the preferred term.

The term knowledge organization systems is intended to encompass all types of schemes for organizing information and promoting knowledge management. Knowledge organization systems include classification schemes that organize materials at a general level (such as books on a shelf), subject headings that provide more detailed access, and authority files that control variant versions of key information (such as geographic names and personal names). They also include less-traditional schemes, such as semantic networks and ontologies. Because knowledge organization systems are mechanisms for organizing information, they are at the heart of every library, museum, and archive.