Keyword proximity refers to closeness of keywords. Your keywords should be close to each other in content of web page. Many people don’t know about keywords. They generally treats key phrases as a keyword. Usually we do not target keyword.
For example: This post is related to “Keyword Proximity”. The word “Keyword Proximity” is not a key word. It is a key phrase. Here “Keyword” is a one keyword and “Proximity” is another keyword.
To make proximity higher you should use both keywords in you content.
Example of “Keyword Proximity”: Keeping your keywords close to each other helps to increase proximity. Here you can see that I am using keyword (Actually key phrase) “Keyword Proximity” in isolated form. Distance between “Keyword” and “Proximity” should be less to make proximity higher. Using your keywords again and again in content is not a good practice. It is called “Keyword Stuffing”. That’s why we should use main keyword in its original form and in isolated form too.