Grain Posted on 13th November 20152nd September 2020 by ThePD (The Project Definition) Grain is 1) a seed or seeds from a plant; 2) an individual crystal in a solid metal or alloy in which the atoms are arranged in an orderly pattern. 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 Substance and tagged food, metal, substance. 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.