Lessons learned is a two word phrase that refers specifically to the project management related input and output device that represents the knowledge, information, or instructional knowings that have been garnered through the process of actually completing the ultimate performance of the respective project. The idea of lessons learned is a valuable one for the reason that when the sum total of all lessons have been factored in, at that point it can be more confidently assumed that these said lessons will benefit future endeavors and ideally prevent any negative happenings from taking place in the future. The sum total of lessons learned can be assessed and itemized at any point during the life cycle of a project, and the list can and should be a running one, with the allowance of any suggested modification at any point throughout. The concept of the lessons learned can also be referred to as the project record. Lessons learned for the most part are customarily included as part of the overall lessons learned knowledge base.
This term is defined in the 3rd and the 4th edition of the PMBOK.
