Latent semantic indexing (LSI) is a concept whereby your site is also assessed on content other than the keywords that you are obviously targeting in the on-page and off-page elements of the site. Partly, this is to combat using keywords to draw traffic to content unrelated to the keywords - as porn, gambling and pharmacy spam sites are inclined to do.

More importantly, its because there is a very high mathematical probability that a site that is genuinely about a specific topic ALSO includes multiple iterations of related words, phrases and terms e.g.;

- nouns, verbs and adjective variations
- word derivations
- synonyms
- hypernyms
- hyponyms

Therefore, the major search engine algorithms' are now applying the concepts of "latent semantic indexing" and taking into account all word relationships within the site. Whilst an algorithm might lack "intelligence," the mathematical model is quite robust and delivers extremely accurate relevancy assessments.

To apply the concept of LSI to your site, its a matter of NOT over-loading your page with primary keywords (spamming) but instead, using variations to more accurately describe your topic or theme; E.g. using the term "SEARCH" the following options appear;

Variations or derived words; searcher, searched, searching,

Synonyms - query, queried, querying, seeking, looking, finding

Hypernym: activity, examination, examine, higher cognitive process, investigate, investigating, investigation, look into, operation, scrutiny, see.
- Synonym: explore, hunt, hunting, look, look for, lookup, research, seek.
- Hyponym: angle, beat about, browse, cast about, cast around, comb, cruise, divine, drag, dredge, exploration, feel, finger, fish, forage, foraging, frisk, frisking, fumble, gather, go, go after, grope, grub, hunt, leave no stone unturned, looking, looking for, manhunt, nose, poke, prospect, pry, pursuance, pursue, pursuit, quest, quest after, quest for, raid, ransack, ransacking, re-explore, rifle, rummage, scan, scour, scouring, seek out, seeking, shakedown, shop, strip-search, surf, want.
- Derived: searcher

Noun
- Hypernym: activity, examination, higher cognitive process, investigating, investigation, operation, scrutiny.
- Synonym: hunt, hunting, lookup.
- Hyponym: exploration, forage, foraging, frisk, frisking, hunt, looking, looking for, manhunt, pursuance, pursuit, quest, ransacking, rummage, scouring, seeking, shakedown.

Verb
- Derived: searcher.
- Synonym: explore, look, look for, research, seek.
- Hypernym: examine, investigate, look into, see.
- Hyponym: angle, beat about, browse, cast about, cast around, comb, cruise, divine, drag, dredge, feel, finger, fish, frisk, fumble, gather, go, go after, grope, grub, hunt, leave no stone unturned, nose, poke, prospect, pry, pursue, quest after, quest for, raid, ransack, re-explore, rifle, rummage, scan, scour, seek out, shop, strip-search, surf, want.

The purpose of the example is to show that there are many ways to describe the same activity, product or service.

How to Apply Latent Semantic Indexing

Implement LSI on your site by thoughtfully including variations, derivations, synonyms, hyponyms and hypernyms of your primary keywords and phrases. You will more effectively convince the Search Engines of your content theme than you would by stuffing multiple iterations of the same primary keywords into those page/s!