A secondary value keyword should be considered second (after primary value keywords) when preparing a keyword research project for any of the three different kinds of websites.
The 3 website types discussed on the Keyword Relationship Chart are:
1. Adsense websites (or websites that focus on revenue gained from any sort of monetization, including CPA networks).
2. Product/Service websites
3. Pre-existing websites requiring reconstruction to accommodate silos.
Please carefully study the Keyword Relationship Chart and find yourself on the map before you start drilling into keywords.