Kaizen is a methodology and a philosophy that is present throughout Lean organizations.
'kai' = change
'zen' = good
Kaizen is often translated into English as "continuous improvement." This means looking for possible small improvements regularly.
Kaizen involves everyone at all levels of an organization in continuous improvement by asking them to look for ways to improve their own work processes. This kind of kaizen is something that occurs on a daily basis and eventually becomes a part of work itself. Kaizen empowers people to test out changes and see if they improve the way things work. People on the manufacturing floor, managers, and executives should all participate in kaizen.
Kaizen generally focuses on slow, incremental changes rather than vast, innovative changes. Some have described this as the difference between the Eastern tortoise and the Western hare. In the Eastern mindset, small changes add up to large improvements over time, while in the West people tend to focus on fast, innovative changes.
In Lean, by continually seeking to improve standards and looking for ways to reduce waste, even when nothing is broken, the system ends up working better in the long run.
Some businesses also have periodic kaizen events. During these events, a team of people spends up to a week focusing solely on improving one process or one part of a process.