Topical authority is the depth and internal coherence of a site's coverage across one subject area. Unlike domain authority, it is subject-specific — a site can hold strong authority on one topic while having none on an adjacent one.
Built through clusters: a pillar page plus supporting articles connected by deliberate internal links.
Coverage gaps within a cluster weaken the whole structure.
It transfers poorly between unrelated topics, which is why unfocused blogs underperform.