Relevance term explained

The measure of similarity of two texts. Usually used in SEO to the search query and the document issued on the request in the results of search engines. For example, "the search engine gave irrelevant documents or incorrectly determined to be relevant to my request page". In the General case, the relevance is computed by the formula:

Similarity = SUM(Wd,t * Wq,t)

Where:

• t is the number of words in the query; 
• SUM operator the sum over all words of the query; 
• Wd,t is the weight of the t-th word in the document; 
• Wq,t is the weight of the t-th word in the query.

Actually relevance in modern search engines take into account the weight of the individual passages and is a more complex formula.

To achieve maximum relevance of the text to request can only be using key words, their synonyms and word forms in the text headers and paragraphs. If one word of the query text not found in document, then we say that the document is totally irrelevant to this request.