Co-Citation
Co-citation is how often two documents get cited together by other documents. Henry Small's 1973 paper defined it as a new way to measure how closely two scientific papers are related, and to group papers by field. In SEO, people use the same word when two businesses or websites keep getting named on the same pages.
Source: Henry Small, Co-citation in the Scientific Literature, Journal of the American Society for Information Science (1973), ERIC record, checked October 29, 2026
What Co-Citation means for your business
In the SEO sense, it's who you get named next to. Say a local paper's list of bakeries worth the drive names you beside two bakeries everyone in town knows, so readers file you with them.
You'll also see it called co-occurrence, or an entity co-occurrence signal. That usually means your name showing up near the words and names that go with your trade, link or no link. SEO writers say search engines read both kinds of pairing. Google hasn't said how, or whether, it uses them, so we'd treat that as a theory. What we can check is what the lists and articles in your field say, and whether you're on them.
We'd look for the pages buyers read when they're weighing options: trade lists, local roundups, review sites and industry directories. If your competitors keep turning up together on those pages and you don't, getting your name onto those pages is where we'd put the work.
Last reviewed October 29, 2026. All terms
How AI answers it today
On October 29, 2026, ChatGPT gave only the research meaning and cited nothing. Google's AI Overview gave both meanings, citing research papers and SEO agency blogs, and said search engines connect sites that get named together, a claim it sourced to SEO blogs, not Google.
Our run through ChatGPT and Google's AI Overview, October 29, 2026. A sample, not what every buyer sees.
Related terms in entities and the knowledge graph
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