Other examples of controlled vocabularies are the Thesaurus of ERIC Descriptors, the Thesaurus of Psychological Terms, and the Thesaurus of Sociological Terms. The following sections describe the different relationships between controlled vocabulary terms. Controlled vocabularies are hierarchical and extensively cross-referenced. Thus we note that reciprocal entries are always required. A chainlike quality is introduced by this policy of structuring.
Some descriptors have particular meanings in fields other than education.
Somewhat akin to Scope Notes are Parenthetical Qualifiers. These are not intended to function as definitions but rather to give focus to the terms to which they are attached. They serve to clarify homographs and ambiguities in word meaning and usage.