Topical authority
Topical authority is the recognition a site earns by covering a subject in depth: pillar pages, sub-topics, related questions, coherent internal linking. It accelerates ranking for each new piece of content added in the same field.
In practice
A site covering fifty facets of a single trade positions faster on the fifty-first than a generalist ever would. This is the argument for clusters: rather than ten isolated articles, a pillar page and its linked satellites. Authority builds field by field, not query by query.