Model Drift
When a model gets worse over time because the world moved on and it did not. A pricing or demand model trained two years ago quietly stops matching how customers behave now.
Related terms
AI Search
Searching by asking a question in ordinary language and getting a written reply, rather than typing keywords and choosing from links. It changes what a website has to do: be readable and quotable by a machine, not just findable.
Topical Authority
Being recognised as a reliable source on a subject rather than on a single keyword, usually by covering it thoroughly and consistently. It is what makes a small site beat a bigger one in a narrow field.
Semantic Search
Search that works on meaning rather than exact words, so a page can match a query it never literally contains. It is why writing naturally now beats repeating a keyword.
Google-Extended
The robots.txt setting that controls whether Google may use your content for Gemini and AI Overviews. It is separate from ordinary Google Search, so you can allow one and refuse the other.
Vector Search
Searching by meaning rather than by matching words. A page that never uses the phrase somebody typed can still be the best answer, and vector search is what finds it.
Crawl Budget
The rough limit on how much of your site a crawler will fetch in a visit. Slow pages and endless near-duplicate URLs spend it on nothing, so the pages that matter get visited less often.