These are the relations that are predefined in the Net Search Extender:
An associative relation is a bidirectional relation between two terms that do not express the same concept but relate to each other.
Predefined associative relation: RELATED_TO
Examples:
tennis RELATED_TO racket football RELATED_TO goal (sports)
A synonym relation is a bidirectional relation between two terms that have the same or similar meaning and can be used as alternatives for each other. This relation can, for example, be used between a term and its abbreviation.
Predefined synonym relation: SYNONYM_OF
Examples:
spot SYNONYM_OF stain US SYNONYM_OF United States
Figure 28 shows two goal terms in the same thesaurus. One is specified with the comment (sports), the other with the comment (abstract). Even if terms have the same spelling, synonym relations can connect different word groups. You can model this by using different relations when defining the thesaurus.
A hierarchical relation is a unidirectional relation between two terms, one of which has a broader (more global) meaning than the other. Depending on its direction, the relation can be used to look up either more specialized or more global terms.
Predefined hierarchical relations:
NARROWER relations are for modelling a sequence of more specialized terms. The deeper you follow a narrowing relation, the more specific the terms become. For example, if you look up the term house along a NARROWER relation, the result could be skyscraper palace church chapel cathedral and so on, in a list of increasingly specialized terms.
BROADER relations are for modelling a sequence of more and more global terms. The deeper you follow such a relation, the less specific the terms become. For example, if you look up the term house along a BROADER relation, the result could be building construction object and so on, in a list of increasingly global terms.