What is keyword density?

Keyword density refers to the percentage of occurrence of a keyword in a webpage out of all the words on that page. For example, if a keyword appears four times in an article of 100 words, the keyword density would be 4%. It is also known as keyword frequency as it talks about the frequency of occurrence of a keyword in a page. There is no ideal or exact keyword density for better ranking. However, the keyword density of 2 to 4 % is considered suitable for SEO.