Terminology is the study of terms and their use. Terms are words and compound words that are used in specific contexts. Not to be confused with "terms" in colloquial usages, the shortened form of technical terms (or terms of art) which are defined within a discipline or specialty field. The discipline Terminology studies among other things how such terms of art come to be and their interrelationships within a culture.
Terminology therefore denotes a more formal discipline which systematically studies the labelling or designating of concepts particular to one or more subject fields or domains of human activity, through research and analysis of terms in context, for the purpose of documenting and promoting correct usage. This study can be limited to one language or can cover more than one language at the same time (multilingual terminology, bilingual terminology, and so forth) or may focus on studies of terms across fields.
Terminology is not connected to information retrieval in any way but focused on the meaning and conveyance of concepts. "Terms" (i.e. index terms) used in an information retrieval context are not the same as "terms" used in the context of terminology, as they are not always technical terms of art.
Ad hoc terminology is prevalent in the translation profession, where a translation for a specific term (or group of terms) is required quickly to solve a particular translation problem.