Stop Words
Common English words (the, a, and, of, to) that are typically filtered out before keyword analysis because they carry little SEO relevance on their own.
Stop words are common, frequently occurring words in a language that carry little semantic weight on their own. In English, examples include "the," "a," "an," "and," "or," "but," "is," "are," "of," "to," "in," "on," "at," "for," "with," "from," "by," and "that." These words make up a large fraction of any natural text — sometimes 30-40% — but they don't carry the topical meaning a search engine (or a reader) is looking for.
SEO density tools filter stop words by default because they would otherwise dominate the keyword table. In a 500-word article about content marketing, the word "the" might appear 50 times, producing a 10% density reading that is meaningless and distracting. By removing stop words before counting, the density table surfaces the actual topic-bearing terms: "content," "marketing," "strategy," "SEO," "audience," and so on.
The standard English stop word list typically includes 120-180 words. The exact list varies between tools (Lucene, NLTK, spaCy, and Yoast each have their own), but the core 100 are nearly universal. Most density checkers and SEO crawlers let you toggle the filter off if you want to see the raw count — useful for tasks like auditing anchor text distribution or measuring how often a target brand name appears relative to other filler.
It's worth noting that stop words are not inherently bad for SEO. They are necessary for natural-sounding prose. The filter is a measurement convenience, not a content recommendation. Google's algorithms understand that "the" and "a" don't carry ranking signal; the filter simply keeps the human reading the density table focused on the words that do.