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LSI (Latent Semantic Indexing)
Latent Semantic Indexing (LSI) is a mathematical technique used in natural language processing to analyze the relationships between terms and the concepts they represent in a corpus of text. In SEO, "LSI keywords" refers to semantically related terms and phrases that naturally co-occur with a primary keyword, helping search engines understand topical relevance — though Google's actual use of strict LSI is debated.
Semantically related keywords are identified using tools like LSIGraph, Google's "Related Searches" and "People Also Ask" features, SEMrush's Keyword Magic Tool (topically related terms), and Ahrefs' "Also rank for" report. Including semantic variants improves topical depth and avoids over-reliance on exact keyword repetition.
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Related Terms
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Keyword Density
Keyword density is the term used to express how often a targeted keyword is used on a web page.
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Keyword Research
The process of discovering, analyzing, and prioritizing the words and phrases potential customers type into search engines and AI assistants — combining search volume, intent, and competitive difficulty into a content-strategy plan.
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Long Tail Keywords
Keywords the user query volumes of which are lower than those of short-tail keywords and usually consist of three or more words are called long-tail keywords.
Technical SEO
TF-IDF
TF measures the keyword density, while IDF measures how many different texts the keyword appears in.