A thesaurus is a controlled and structured vocabulary where concepts are represented by labels. In the context of the EU Vocabularies, a thesaurus is a multilingual equivalent of the previous basic definition, where the same concept in each of the supported languages is represented by a single preferred label. Potentially, one or several alternative labels can also be linked to each language version of a concept.
In parallel to the preferred and alternate labels, each concept can be semantically related within the thesaurus following three possible correspondences: a given concept can have broader, narrower or an associative relationship with other concepts.
Within a single thesaurus, a number of micro-thesauri can be defined.
Finally, thesauri can be linked through the alignment of specific concepts from each of them. The alignments that can be defined between concepts of separate thesauri fall into the following scope of correspondences:
- Has exact match
- Has close match
- Has broad match
- Has narrow match
- Has related match