Muda is waste: activity that consumes resources without producing anything the customer would pay for. The conventional grouping is eight types.
- Transport — moving material that did not need moving
- Inventory — stock beyond what the flow requires
- Motion — people moving unnecessarily to do the work
- Waiting — work sitting idle between steps
- Overproduction — making more, or earlier, than needed
- Overprocessing — doing more than the customer values
- Defects — work that must be corrected or scrapped
- Unused talent — capability nobody asks for
Overproduction is usually treated as the worst because it manufactures the others: too much output becomes inventory, which needs transport, which conceals defects until they are expensive.
Not everything without customer value is waste to remove. Regulatory inspection and safety checks add nothing the customer would pay for and cannot go — the working distinction is between waste, which is a target, and necessary non-value-adding work, which is a constraint to keep small.
Waste-hunting also has a failure mode of its own. Eliminating waste at a step that is not the constraint changes nothing about what the system produces, and a team asked to find waste will always find some.
