Originally Posted by ArcadeJunky

Keyword Density

A classic SEO topic is keyword density, which is simply a percentage measure of how frequently the keyword appears in the text of a page. Sometimes a higher density will make pages rank higher for a particular keyword, but taking it too far can be penalized. The best approach is write for the human reader, by making your copy natural and readable without much artificial manipulation of the density. Keep in mind synonyms for your keywords and use them in the text, as people may search for the same thing in many ways with different words.