Keyword density
Keyword density is the percentage of times a keyword or phrase appears on a web page compared to the total number of words on the page.

Google recommends 1 to 3 percent keyword density for a web page. Using a keyword more than that could be a reason of search spam.

The formula to calculate the keyword density on a webpage is:

(NKr / TKn) * 100

Where NKr is how many times you repeated a specific keyword
And TKn is total words available on that webpage.

When calculating the density of a keyword phrase, the formula would be
(Nkr * Nwp / Tkn) * 100,

Where Nwp is the number of words in the phrase
For example for a page about search engine optimization where that phrase is used four times in the webpage and total number of words in the webpage are 400. The phrase is contains 3 words only.
Then Keyword Density is: (4*3/400)*100 = 3 percent

Keyword Proximity
Keyword proximity is the closeness between two or more words. In general, the closer the keywords are the better.
For example:
    Best companies for SEO in India
    Best SEO companies in India
In the above example, if someone searched for "best seo companies" a web page containing the second sentence is more likely to rank higher than the second.
The reason is because the keywords are placed closer together.

 Keyword Prominence

In search engine optimization it refers to the prominent placement of keywords or keyphrases within a webpage. It means, your keywords should be at prominent area in content of your web pages. To make higher prominence, you need to keep your keywords close to html tags such as or , , , , <p> , <br>, <h1> or <h2> <br><br>By practicing this method of optimization, you create weightage of your web page by keywords. Keep in mind that you should not target unique keyword on every page. While targeting keyword on page, you should follow right method of keyword targeting.<br>You can place keywords at:<br>1.    Title<br>2.    Headings<br>3.    Top of paragraph<br>4.    Beginning of a sentence<br>5.    Start of a webpage<br><br></p> </div>