a corpus can be subdivided into an unlimited number of parts called subcorpora. Subcorpora can be used to divide the corpus by the type (fiction, newspaper), media (spoken, written) or time (e.g. by years) or by any other criteria. A subcorpus can also be created from a concordance by including all concordance lines and the documents they come from into a subcorpus.
A subcorpus can be selected on the advanced tab of most of the tools (except for word sketch differences and thesaurus). Selecting a corpus will restrict the search or the analysis to only this subcorpus.