Prevalence Posted on 14th December 201512th May 2021 by ThePD (The Project Definition) Prevalence is 1) the fact of something existing or happening often; 2) the frequency of a disease may be measured. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in HSE and tagged health. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.