Kaizen -

A Team Activity through which continuous improvement is sought. The original term means "change for the better" It was pioneered by the Japanese and is now mainstream for companies who practice continuous improvement.

Lean -

lean production : A philosophy of production that emphasizes the minimization of the amount of all the resources (including time) used in the various activities of the enterprise. It involves identifying and eliminating non-value-adding activities in design, production, supply chain management, and dealing with the customers. Lean producers employ teams of multiskilled workers at all levels of the organization and use highly flexible, increasingly automated machines to produce volumes of products in potentially enormous variety. It contains a set of principles and practices to reduce cost through the relentless removal of waste and through the simplification of all manufacturing and support processes. Syn: lean, lean manufacturing

Six Sigma -

A methodology that furnishes tools for the improvement of business processes. The intent is to decrease process variation and improve product quality.