Facet analysis consists in an analysis of a subject in its entirety into a certain number of facets or categories of things; within each category, the subject headings enumerated all possess the same relationship vis-&-vis the subject in its entirety.

Foskett Classification and indexing in Science, p. 42; As cited in: Eric de Grolier (1962) A study of general categories applicable to classification and coding in documentation. p. 15