Keyword density is the measurement in percentage, the number of times a keyword or phrase appears compared to the total number of words in a page. In the context of search engine optimization keyword density can be used as a factor in determining whether a web page is relevant to a specified keyword or keyword phrase.
So what does this mean to us several things.
First of all you need to remember anything done in excess is spam and spam is bad.
You also need to know that good use of keywords helps you get more hits. Example:
Say you are selling a Red White and Blue Die Cast Motorcycle made by Hot Wheels from say the 1970's its name is "Freedom Rocket" its in Very Good condition with minor wear if any paint not chipped, its still bright and vibrant looking, and what ever else you can think of to describe it.
Now you have to come up with keywords that the common average user will look for.
So we know that it is what?
1. Die Cast Toy
3. Type of Toy
6. Vintage Toy
7. Name of Toy
8. Material its made of
I can go on but lets use these.
Now Think of these as attributes as well. Everyone should have already made a copy of all the attributes ecrater uses for google, if not get it!
in the attributes we can use up to 15 so if you can think of 15 do it, the more keywords You can use the better.
so 1. can be Brand= Hot Wheels
2. department= Vintage Toys, Die Cast, Toy Cars (what ever you use for the category you made) I use Die Cast Toys
3. edition= Freedom Rocket
4. Style= Motorcycle
5. format =1/16 scale
6. color= red, white, blue
7. feature= USA Flag
8. genre= Collector
9. height= 1 inch
10. length= 2 inches
11. Made_in: Malaysia
12. material+ metal
All of those are keywords
All of them relevant to the item being sold, and all usable in your title
My Title would read something like this
Vintage 1970 Hot Wheels Freedom Rocket Motorcycle Die Cast Toy Red White Blue Malaysia
Now that I have my title I need to describe the item, other than the Title, and attributes there is one other time to get your key words in and that is to copy your title as the first sentence of your description. Google states that they use the first sentence of each item to decipher keywords, If you have a bunch of the, and's and buts in there those dont work they need to see your keywords and the most effective way to do that without spamming is to use them in the first sentence of your paragraph describing the product.
You now have three placements of valuable keywords in your items page.
Effective and easy.
Hope this helps everyone.