an alphabetical list of words relating to a specific subject, text, or dialect.

Keyword Density

Described either as a number or a percentage, it represents the frequency at which a keyword or a phrase should appear in the content of a webpage, in comparison to the total number of words on that page.

Formula to calculate keyword density is 

(Nkr/Tkn)*100, where

Nkr = no. of times a specific keyword was repeated

Tkn = total no. of words in the text to be analysed

For determinig Keyword Phrase Density 

(Nkr*Nwp/Tkn)*100, where

Nwp = the no. of words in a specific phrase