Website SEO: Explaining LSI

Website SEO has changed a lot in the past few years. A lot of that is because of Google — see our previous three posts for more on that — but another lot of is because SEO folks have expanded quite a bit on their own understanding of how search engines work. The rise and fall of metadata structures (which do still exist, but frankly few people care) is attributable largely to the fact that people realized they didn’t need them. What they needed was a clearer comprehension of Latent Semantic Indexing (LSI).

When LSI first became part of Google’s arsenal back in 2004, it was dramatically misunderstood. People thought it meant “you have to add other keywords that are like your normal keyword only different.” For example, if your keyword was “Los Angeles SEO,” you might also add “LA SEO” and “Los Angeles SEM” and so on. Or if it was “Run faster,” you might add “running faster” or “Run more quickly.”

As it turns out, that was entirely wrong, not just about what LSI looks for on your site, but about its purpose in the first place.

LSI: A One-Sentence Description

  • LSI is an algorithm that determines, using other key phrases in the vicinity of a given ambiguous word, which of the multiple potential meanings that ambiguous word has.

In other words, LSI only matters if your keyword of choice is ambiguous. Now, a lot of words are ambiguous. “Run faster,” for example — “run” can mean “to propel yourself forward by moving your legs quickly,” or “a long vertical flaw in your pantyhose,” or “a string of repetitions of a given event or item,” or a few other things. “Faster” can mean “more quickly than,” or “held more tightly than,” or “further ahead of the correct time than,” and so on. So LSI is really really important to getting the correct search results for a lot of search terms.

“Los Angeles SEO” on the other hand, is almost entirely unambiguous. (There is another place in the world called ‘Los Angeles,’ but it’s an unincorporated crossroads in southern Texas most famous for being ‘that place with the barbeque stand in the middle of nowhere.’) There’s no amount of LSI that will ever affect that search term, because Google knows what you mean.

If LSI Doesn’t Matter to SERPs, What Does?

That’s easy: grammar! Come back next week, and we’ll show you what we mean.