Continuous improvement glossary

The terms of Lean and Six Sigma, each defined in one sentence, with a link to the full guide where there is one.

5S: A method to organise a workplace in five steps: sort, set in order, shine, standardise and sustain.
5 Whys: A root-cause technique that asks “why?” repeatedly until it reaches a cause a concrete action can remove. Read the guide →
A3: A way of solving a problem on a single A3 sheet, from background and current state to root cause, countermeasures and follow-up. Read the guide →
Control plan: The document that keeps an improvement in place: which step to watch, with which metric and limits, how often, who acts and what they do if it drifts. Read the guide →
DMAIC: The Six Sigma method for improving an existing process in five phases: Define, Measure, Analyse, Improve and Control.
Gemba: The place where the work is done; “going to the gemba” means observing the process there rather than from reports.
Ishikawa diagram: A fishbone-shaped diagram that groups the possible causes of a problem into categories such as method, manpower, machine and material. Read the guide →
Kaizen: Continuous improvement through small, frequent changes; a kaizen event is a focused workshop of a few days on one process. Read the guide →
KPI: Key performance indicator: the metric that shows whether a process or project is reaching its goal. Read the guide →
Lead time: The total time from the moment a request enters a process to the moment it leaves, waiting included.
Lean: A way of managing work that increases value for the customer by removing waste from the process.
Muda (waste): Any activity that consumes resources without adding value for the customer; Lean names eight kinds. Read the guide →
Pareto chart: A bar chart that ranks causes from most to least frequent, to show the few that account for most of the effect. Read the guide →
PCE (process cycle efficiency): The share of the lead time spent on work that adds value: value-adding time divided by lead time.
PDCA: The improvement cycle Plan, Do, Check, Act, repeated to test a change and make it standard.
Poka-yoke: A simple device or design that makes a mistake impossible, or makes it visible at once.
Project Charter: The one-page document that launches an improvement project with its problem, goal, scope, team and milestones. Read the guide →
Process time: The time a step spends actually working on the unit, without waiting.
SIPOC: A one-page map of a process listing its suppliers, inputs, main steps, outputs and customers. Read the guide →
Six Sigma: An approach to improvement that reduces variation and defects in a process, using data and the DMAIC method.
Takt time: The pace at which a unit must be finished to meet customer demand: available time divided by demand.
Value stream map (VSM): A map of every step of a process with its times, stock and waiting, used to see where the lead time goes. Read the guide →
Voice of the customer (VOC): What customers say they need, turned into measurable requirements for the process. Read the guide →