The raw density index and the weighted density index are two different measures of the frequency of a keyword in a text. The main difference between these two measures is that the raw density index gives more importance to the total length of the text (in terms of words), while the weighted density index gives more importance to the structure of the text (in terms of sentences). Thus, a text with many occurrences of a keyword but also many words in general might have a low raw density index but a high weighted density index if the keyword is concentrated in a small number of sentences. This can be useful for understanding how a keyword is distributed in a text.