A terminological dictionary is a dictionary whose entries are constituted by the elements of a terminology. Thus, each lemma is a term.

The microstructure of a terminological dictionary usually comprises the following items:

• analysis of the term (language of origin, formation, meaning of the components); since most contemporary technical terms are modern formations, this is not really an etymology
• equivalent terms in other languages (many terminological dictionaries are, to that extent, multilingual)
• major subdivision of the entry by different acceptations of the term in the history of the discipline or in competing schools
• tracing back of the term to its first use in some work by some scientist
• explanation of the meaning (for each of the acceptations)
• cross-reference to systematically related terms
• bibliographical references.

Since a term has to be a common noun, the lemmas of a terminological dictionary are common nouns. However, most professional fields have technical expressions that are verbs or adjectives, like in linguistics the ones in the left column of the following table. In such cases, the expression is lemmatized under the corresponding abstract noun, thus:

As the examples show, the abstract noun is in some cases derived from the non-noun base; in other cases both the noun and the non-noun are derived. Often, especially in the former case, the meaning of the verb or adjective is conceptually simpler than the meaning of the abstract noun. In such cases, one defines the simpler term, as in this example:

synonymy: A linguistic expression is synonymous with another linguistic expression iff both have the same meaning. This is operationalized as free variation, i.e. substitutability without difference in all contexts.
Synonymy is the relation of being synonymous.

The last sentence of the example definition is normally superfluous, because the kind of derivation involved in such pairs as synonymous – synonymy is mostly regular, so the user who gets synonymous defined under the lemma synonymy can infer what the latter is.

While any dictionary has, by its very nature, some standardizing function, this is possibly most prominent in a terminological dictionary. This is because science and technology are more in need of standardization of their concepts than other domains.

A comprehensive treatment of the structure of a terminological network, applied to linguistics, is found in Lehmann 1996 and on the website Relationen zwischen Begriffen und Begriffssysteme.

References

Lehmann, Christian 1996, "Linguistische Terminologie als relationales Netz". Knobloch, Clemens & Schaeder, Burkhard (eds.), Nomination - fachsprachlich und gemeinsprachlich. Opladen: Westdeutscher Verlag; 215-267.