| link churn | The measurement of lost links within a specified time period. |
| infographic | Noun. A large, oversized image in which many purported facts have been embedded in a stylized format. The intent of the infographic is to encapsulate useful, interesting information in an easy-to-read manner. Infographics cannot be indexed by search engines but they have given rise to Infographic Spam (q.v.). |
| host | Noun. A much-used term in academic search engineering literature to distinguish between Web document collections on a systemic level. A host is not necessarily the same as a site. Hosts are generally defined to be either entire domains (example.com) or sub-domains (sub1.example.com). A domain to which one or more sub-domains belong would be treated as multiple individual hosts, distinct from one another. A host is easier to identify than a Web site, which may be only a part of a hosts content. |
| quality score | Quality score is Googles measurement for the quality of an ad and is based on a handful of factors, including: expected click through rate from the SERP, the relevance of the ad to the keyword, relevance of the landing page to the ad and keyword |
| conceptual links | some of the more advanced search engines are attempting to understand links beyond focusing on the anchor text, for example by using co-citation. |
