Ries positions the tenets of The Lean Startup on the ideas of lean manufacturing, lean thinking, and lean user experience (UX). These concepts pervade the text as unifying principles to justify the efficacy of validated learning, small batch production, and engines of growth. Thus, the concept of lean, as an adjective applied to diverse business philosophies, acts as a unifying theme throughout the text to communicate Ries’s recommendations for startup success. All these lean concepts come from other authors and business minds: lean manufacturing was developed by Taiichi Ohno and Shigeo Shingo, lean thinking by James P. Womack and Daniel Jones, and lean UX by Jeff Gothelf and Josh Seiden. Ries synthesizes these authors’ theories and applies it specifically to the systems and operations of a startup. Ries expands upon the concept of lean in the Lean Startup method by developing new business principles: Build-Measure-Learn feedback loops, MVPs, validated learning, innovative accounting, pivot (or persevere), and portfolio thinking. Although these principles may occur at separate stages in the startup’s operations, all of them embody lean in their essential functions and outcomes. Speed and agility in development characterize the central functions of lean in startup organizations, while growth and sustainability exemplify the outcomes.