Clusters refer to a content organization model where you create one comprehensive pillar page on a broad topic, then build multiple supporting cluster pages that cover specific subtopics in detail. Each cluster page links back to the pillar, and the pillar links out to all clusters, forming a tight internal linking structure that signals topical depth to search engines. For example, if your pillar page is about "Commercial Real Estate in Ottawa," your cluster pages might cover "Office Space Lease Rates Downtown Ottawa," "Retail Property Investment Returns," or "Zoning Requirements for Commercial Buildings." Each cluster targets long-tail keywords while reinforcing the pillar's authority on the broader topic. The model works because Google has shifted from keyword-matching to understanding topics and semantic relationships. When you interlink 8-15 related pages around one pillar, you demonstrate expertise across that subject area. This typically lifts rankings for both the pillar and cluster pages compared to orphaned standalone articles. Practical build considerations: Your pillar should be 2,000-4,000 words covering the topic broadly without going too deep. Clusters run 800-1,500 words each, diving into specifics the pillar only mentions. Use descriptive anchor text in your interlinks, not generic "click here" phrases. The pillar URL should be short and obvious, like /commercial-real-estate/, while clusters nest logically under it or use clear descriptors. At Ottawa SEO, we map clusters before writing. We identify 10-20 questions or subtopics users actually search for using keyword tools and Google autocomplete, prioritize by search volume and competition, then assign one cluster per subtopic. We avoid forcing the model where it doesn't fit. If your site has 30 unrelated service pages, calling them a cluster doesn't make it true. The content must genuinely relate and support a shared parent topic, or the structure adds complexity without SEO benefit.