Lean Six Sigma Glossary
Lean Six Sigma has its own language, borrowed from statistics, from the Toyota Production System and from quality standards. This glossary explains the terms you will hear on a project team, in a Kaizen event or during an audit, in plain English. Each definition is short on purpose. When you are ready to use these tools on real work, our Belt programs teach them step by step, and our consultants apply them alongside your team.
Not sure where to start? Take a look at our Which Belt guide.
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5S
5S is a method for organizing a workspace so that the right things are in the right place and problems are easy to spot. The five steps are Sort, Set in Order, Shine, Standardize and Sustain, from the Japanese words seiri, seiton, seiso, seiketsu and shitsuke. It works in offices and hospitals as well as on factory floors. Many teams treat 5S as the foundation that makes other Lean tools possible.
5 Whys
The 5 Whys is a simple way to dig past a symptom by asking "why did this happen?" again and again until you reach a cause you can actually fix. Five is a rule of thumb, not a fixed number. It works best for straightforward problems and is often paired with a fishbone diagram when there may be several causes. Root cause tools like this are part of our Lean Six Sigma Belt programs.
8 Wastes
The 8 Wastes are the common kinds of activity that use time and money without adding value for the customer. A popular memory aid is DOWNTIME: Defects, Overproduction, Waiting, Non-utilized talent, Transportation, Inventory, Motion and Extra processing. Learning to see these wastes is usually the first skill in any Lean program. See also Muda.
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A3
An A3 is a one-page problem-solving report named after the 11 by 17 inch paper size it was first written on. It tells the story of a problem from left to right: Background, current state, goal, root cause, countermeasures and follow-up. The point is not the form itself but the clear thinking and coaching conversations it encourages. Lean problem-solving methods like this are part of our Lean and Kaizen training.
Andon
Andon is a signal, such as a light, a sound or a cord, that lets anyone call for help the moment a problem appears. The idea is to stop and fix small problems right away instead of passing them downstream. A good andon system depends on leaders who respond quickly and without blame.
APQP (Advanced Product Quality Planning)
APQP is a structured framework, widely used in the automotive industry, for planning a new product and its manufacturing process so that it meets customer requirements from the first production run. It moves through phases from planning and design to process validation and feedback. Common outputs include design and process FMEAs, control plans and the PPAP submission.
AS9100
AS9100 is the quality management system standard for the aviation, space and defense industries. It is built on ISO 9001 and adds requirements for things like product safety, configuration management, counterfeit part prevention and on-time delivery. Many aerospace primes require their suppliers to hold AS9100 certification.
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Black Belt
A Lean Six Sigma Black Belt is an experienced practitioner who leads complex, cross-functional improvement projects and coaches Green Belts. The Belts build on each other, and Black Belt is required before Master Black Belt. Our Black Belt program includes 1:1 mentorship from a Master Black Belt.
Bottleneck
A bottleneck is the step in a process with the least capacity, which limits how much the whole process can produce. Speeding up any other step will not raise total output until the bottleneck improves. Finding it is often the quickest way to shorten lead time.
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CAPA (Corrective and Preventive Action)
CAPA is a quality system process for investigating problems, fixing their root causes and preventing them from happening again or happening in the first place. Corrective action responds to a problem that has already occurred; preventive action addresses a risk before it causes one. Regulators and auditors in medical device, pharmaceutical and aerospace settings pay close attention to how well CAPAs are investigated and closed. Root cause analysis is central to strong CAPA work, and it is covered in our Lean Six Sigma Belt programs.
Champion
A Champion, sometimes called a sponsor, is the leader who owns the business reason for a project. The Champion picks or approves the project, removes roadblocks and makes sure the team has time and resources. Projects with an active Champion are far more likely to stick.
Control Chart
A control chart is a time-ordered graph of process data with a center line and upper and lower control limits calculated from the data itself. It helps you tell normal, everyday variation apart from unusual signals that deserve investigation. Different chart types exist for different kinds of data, such as I-MR, X-bar and R, p and u charts.
Control Plan
A control plan documents how an improved process will be monitored: What is measured, how often, by whom, the acceptable limits and what to do if a limit is exceeded. It is the main deliverable of the Control phase of DMAIC and a required APQP output. Without one, gains tend to fade.
COPQ (Cost of Poor Quality)
Cost of poor quality is the money lost because work was not done right the first time. It includes internal failures like scrap and rework, external failures like returns and warranty claims, and the cost of extra inspection. Putting a number on COPQ is often how an improvement project earns leadership support.
Cp and Cpk
Cp and Cpk are process capability indices that compare how much a process varies with how much variation the customer specification allows. Cp looks only at spread, while Cpk also accounts for whether the process is centered between the limits. A higher value means fewer parts or transactions outside specification, and many industries set a minimum Cpk for suppliers. Process capability is covered in our Lean Six Sigma Belt programs.
CTQ (Critical to Quality)
A CTQ is a measurable characteristic of a product or service that the customer considers essential. Teams turn vague customer statements, such as "I want it fast," into specific CTQs, such as "delivered within two business days." CTQs keep a project focused on what the customer actually values.
Cycle Time
Cycle time is how long it takes to complete one unit of work at a step or across a process, from start to finish. It is often compared with takt time to see whether a process can keep up with demand. Be sure to define the start and stop points, because teams frequently measure it differently.
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Defect
A defect is any output that fails to meet a customer requirement. A single product can have more than one defect, which is why Six Sigma separates defects from defective units. Reducing defects is one of the main goals of Six Sigma.
DMADV
DMADV is a Six Sigma roadmap for designing a new product or process rather than fixing an existing one. The phases are Define, Measure, Analyze, Design and Verify. It is the core method of Design for Six Sigma and is used when a current process cannot be improved enough to meet requirements.
DMAIC
DMAIC is the five-phase roadmap Six Sigma teams use to improve an existing process: Define, Measure, Analyze, Improve and Control. Each phase has clear deliverables, so the team does not jump to solutions before it understands the problem and its causes. DMAIC is covered in our Lean Six Sigma Belt programs.
DOE (Design of Experiments)
Design of experiments is a planned way to test several process inputs at the same time and learn which ones really drive the output. It is far more efficient than changing one factor at a time and can reveal how factors interact. Statistical tools like DOE are covered in our Lean Six Sigma Belt programs.
DPMO (Defects per Million Opportunities)
DPMO measures how many defects a process would produce for every million chances to make one. It lets you compare processes of very different complexity on the same scale. DPMO can be converted to a sigma level, which is where the name Six Sigma comes from.
Ready to put DMAIC to work? Our Green Belt isn't a certificate mill. You earn certification by passing the exam with 80% or higher and completing a real improvement project. Explore Green Belt.
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Fishbone Diagram
A fishbone diagram, also called an Ishikawa or cause and effect diagram, is a brainstorming tool for organizing the possible causes of a problem. The problem sits at the head of the fish, and causes branch off in categories such as people, methods, machines, materials, measurement and environment. It helps a team think broadly before testing which causes are real.
Flow
Flow means work moves through a process steadily, without stopping, waiting or backtracking. Lean teams create flow by removing delays, shrinking batch sizes and balancing work between steps. Good flow usually shortens lead time and exposes problems faster.
FMEA (Failure Mode and Effects Analysis)
FMEA is a structured way to look ahead and ask what could go wrong with a design or process, what the effect would be and how likely it is to be caught. Each failure mode is scored for severity, occurrence and detection so the team can focus on the biggest risks first. Design FMEAs and process FMEAs are standard in automotive, aerospace and medical device work and connect closely to ISO 14971 risk management.
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Gage R&R
Gage R&R (repeatability and reproducibility) is a study that checks whether your measurement system is trustworthy. It shows how much of the variation you see comes from the measuring tool and the people using it rather than from the parts. If the measurement system is poor, decisions based on its data will be too.
Gemba
Gemba is a Japanese word meaning "the real place," the spot where value is actually created. Going to the gemba means leaders and teams observe the work firsthand instead of relying on reports. A gemba walk is a regular, respectful visit to see the process, ask questions and learn.
Green Belt
A Lean Six Sigma Green Belt can lead improvement projects within their area using DMAIC and core statistical tools, while usually keeping their regular job. Green Belts often support larger Black Belt projects too. The Belts build on each other, so Green Belt is the next step after Yellow Belt.
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Heijunka
Heijunka means leveling production, smoothing out both the volume and the mix of work over time instead of building in large, uneven batches. Leveling reduces the peaks and valleys that cause overtime one week and idle time the next. It is a key part of making a pull system work.
Histogram
A histogram is a bar chart that shows how often values fall within certain ranges. It gives a quick picture of a process's center, spread and shape, and can reveal skew or multiple peaks. It is one of the seven basic quality tools.
Hoshin Kanri
Hoshin kanri, also called policy deployment or strategy deployment, is a method for connecting a few breakthrough goals at the top of an organization to the daily work of every team. Goals are refined through "catchball," a back-and-forth conversation between levels. Regular reviews keep the plan on track and adjust it as conditions change.
Hypothesis Testing
Hypothesis testing is a set of statistical methods for deciding whether a difference you see in data is real or could easily be due to chance. Common tests include t-tests, ANOVA and chi-square tests. In DMAIC it is used mainly to confirm root causes before a team invests in solutions.
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ISO 9001
ISO 9001 is the international standard for quality management systems. It sets requirements for how an organization understands customer needs, controls its processes, manages risk and improves over time, without dictating exactly how to do it. It is the base standard for several industry versions, including AS9100.
ISO 13485
ISO 13485 is the quality management system standard for medical device manufacturers and their suppliers. It is closely related to ISO 9001 but places more weight on regulatory requirements, documentation, risk management and design controls. Medical device regulators in many countries recognize or align with it.
ISO 14971
ISO 14971 is the international standard for applying risk management to medical devices across their full life cycle. It describes how to identify hazards, estimate and evaluate risks, put controls in place and monitor how well they work after release. Tools such as FMEA are often used to support it.
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Jidoka
Jidoka is the Lean principle of building quality in by stopping the process automatically or manually the moment an abnormality occurs. It keeps defects from moving forward and frees people from watching machines. Along with just-in-time, it is one of the two pillars of the Toyota Production System.
Just-in-Time (JIT)
Just-in-time means making and delivering what is needed, when it is needed and in the amount needed. It reduces inventory and exposes problems that large stockpiles tend to hide. JIT relies on tools like pull systems, kanban and short changeovers.
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Kaizen
Kaizen is a Japanese word usually translated as "change for the better." It describes the habit of making small, ongoing improvements, led by the people who do the work. The term is also used for a focused improvement workshop, covered under Kaizen Event.
Kaizen Event
A kaizen event, also called a rapid improvement event, is a short, intense workshop, often three to five days, where a cross-functional team improves one specific process. The team maps the current state, finds waste, tests changes and puts new standards in place before the week ends. Our instructors have led over 1,000 Kaizen events, and kaizen events are part of our Lean and Kaizen training.
Kanban
Kanban is a signal, often a card, bin or digital board, that tells a process when to produce or move more work. Because work starts only when there is a signal, kanban limits overproduction and keeps inventory in check. In knowledge work, kanban boards also limit the amount of work in progress.
Our instructors have led over 1,000 Kaizen events. Learn to run your own with the Kaizen Facilitator Training Program.
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Lead Time
Lead time is the total time from when a customer asks for something to when they receive it, including all the waiting in between. In most processes, waiting makes up most of the lead time. That is why Lean focuses on flow and not only on speeding up individual tasks.
Lean
Lean is an approach to improvement that focuses on delivering what customers value with the least waste of time, effort and materials. It grew out of the Toyota Production System and is now used in healthcare, government, finance and every kind of manufacturing. Lean relies as much on respect for people and daily problem solving as it does on tools.
Leader Standard Work
Leader standard work is a short, written routine of the checks, gemba walks, huddles and coaching that a leader does every day or week. It makes good leadership habits visible and repeatable, and keeps attention on sustaining improvements. Leadership habits like this are part of our Lean and Kaizen training.
Lean Six Sigma
Lean Six Sigma combines Lean's focus on waste and flow with Six Sigma's focus on reducing variation using data. Together they help teams make processes faster, more consistent and less costly. Training is organized into Belt levels, explained in our Which Belt guide.
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Master Black Belt
A Master Black Belt is the most senior Lean Six Sigma practitioner, who coaches Black and Green Belts, guides project selection and helps shape an organization's improvement strategy. Black Belt is required before Master Black Belt. Our Master Black Belt program includes 1:1 mentorship from an experienced Master Black Belt.
Muda, Mura and Muri
Muda, mura and muri are three Japanese words that describe the main enemies of a good process. Muda is waste, meaning activity that adds no value. Mura is unevenness, such as swings in workload, and muri is overburden, asking people or equipment to do more than they reasonably can. Uneven and overloaded processes tend to create waste, so Lean teams tackle all three together.
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Nadcap
Nadcap is an industry-managed accreditation program for special processes in aerospace and defense manufacturing, such as heat treating, chemical processing, welding and nondestructive testing. It is administered by the Performance Review Institute on behalf of major aerospace companies. Suppliers that perform these processes are often required to hold Nadcap accreditation for each process they run.
Nonconformance
A nonconformance is any product, process or record that does not meet a stated requirement, whether that requirement comes from a customer, a standard or an internal procedure. Quality systems require nonconforming items to be identified, contained and reviewed. Serious or repeated nonconformances usually lead to a CAPA.
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OEE (Overall Equipment Effectiveness)
OEE measures how well a machine or line is used compared with its full potential. It multiplies three factors: Availability (was it running?), performance (was it running at full speed?) and quality (were the parts good?). Breaking OEE into these parts shows where the biggest losses are.
Operational Definition
An operational definition spells out exactly how something will be measured, including what counts, where the start and stop points are and what tool is used. It makes sure two people measuring the same thing get the same answer. Weak operational definitions are a common reason project data cannot be trusted.
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Pareto Chart
A Pareto chart is a bar chart sorted from the largest category to the smallest, often with a line showing the cumulative percentage. It reflects the idea that a few causes usually account for most of the problem. Teams use it to decide where to focus first.
PDCA (Plan, Do, Check, Act)
PDCA is a simple, repeating cycle for learning and improvement: Plan a change, try it, check the results and then act by adopting, adjusting or abandoning it. It is also written PDSA, with "Study" in place of "Check." PDCA sits underneath A3 thinking, kaizen and most daily problem solving.
Poka-Yoke
Poka-yoke is Japanese for "mistake-proofing." It means designing a process or product so that errors are impossible, or at least obvious right away, such as a plug that only fits one way. Poka-yoke is usually more reliable than inspection or reminders to be careful.
PPAP (Production Part Approval Process)
PPAP is a standard package of evidence, used mainly in automotive supply chains, that shows a supplier's production process can consistently make parts that meet every customer requirement. It typically includes design records, FMEAs, control plans, measurement system studies, capability results and sample parts. The customer must approve the PPAP before full production shipments begin.
Process Capability
Process capability describes how well a stable process can meet its specification limits. It is usually expressed with indices such as Cp, Cpk, Pp and Ppk. A process must be stable, as shown on a control chart, before its capability numbers mean much.
Process Map
A process map is a diagram of the steps, decisions and handoffs in a process. Mapping a process as it really works, not as the procedure says it works, often reveals rework, delays and unnecessary steps. Swimlane maps add who does each step.
Project Charter
A project charter is a short document that launches an improvement project. It states the business case, problem, goal, scope, team and timeline, and it is signed off by the Champion. A clear charter prevents scope creep and keeps the team and leaders aligned.
Pull System
In a pull system, work is started only when the next step or the customer signals a need, rather than being pushed out based on a forecast. Pull limits overproduction and inventory. Kanban is the most common way to run a pull system.
Facing a stubborn quality problem, a CAPA backlog or an audit finding? Our clients average 10x ROI. Talk to a Master Black Belt.
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Root Cause Analysis
Root cause analysis is a set of methods for finding the underlying reason a problem happened, so it can be fixed for good rather than patched. Common tools include the 5 Whys, fishbone diagrams, Pareto charts and hypothesis tests. It is at the heart of DMAIC, A3s and CAPA investigations. Need help with a stubborn problem? Talk to our team.
Run Chart
A run chart plots data over time in the order it occurred, usually with a median line. It is a simple way to see trends, shifts and cycles. When you add calculated control limits, it becomes a control chart.
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Sigma Level
Sigma level is a way to express how well a process performs, based on how many standard deviations fit between the process average and the nearest specification limit. A higher sigma level means fewer defects. A "six sigma" process is commonly described as producing about 3.4 defects per million opportunities.
SIPOC
SIPOC stands for Suppliers, Inputs, Process, Outputs and Customers. It is a high-level, one-page view of a process used early in a project to agree on its boundaries and who is involved. Teams usually build a SIPOC in the Define phase of DMAIC.
Six Sigma
Six Sigma is a data-driven method for improving processes by reducing variation and defects. It follows structured roadmaps such as DMAIC and DMADV and uses statistics to confirm causes and results. Practitioners are trained at Belt levels from White Belt to Master Black Belt.
SMED (Single-Minute Exchange of Die)
SMED is a method for cutting changeover time, the time it takes to switch a machine or process from one product to the next. The key idea is to move as much setup work as possible to before or after the machine stops. Shorter changeovers make smaller batches practical.
SPC (Statistical Process Control)
Statistical process control is the use of control charts and related tools to monitor a process in real time and react before it produces defects. It focuses on catching unusual variation early rather than inspecting finished output. SPC is a common part of control plans in regulated manufacturing.
Standard Work
Standard work is the current best known way to do a task, written down with the sequence, timing and expected inventory. It is not meant to be fixed forever; it is the baseline that the next improvement builds on. Without standard work, it is hard to tell whether a change actually helped.
Supervisor Boot Camp
Our Process Improvement Boot Camp for Supervisors is a 21-hour process improvement program for supervisors. It is available self-paced, live online or in person. See the Supervisor Boot Camp.
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Takt Time
Takt time is the pace at which a process must produce to meet customer demand. You calculate it by dividing the available working time by the number of units the customer needs in that time. Comparing cycle time with takt time shows whether a process can keep up or needs to be rebalanced.
TPM (Total Productive Maintenance)
Total productive maintenance is an approach that makes operators and maintenance staff partners in keeping equipment running reliably. Operators handle routine cleaning, checks and small adjustments, while maintenance focuses on planned and preventive work. TPM is often measured using OEE.
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Value Stream Map (VSM)
A value stream map is a diagram of all the steps, material flows and information flows needed to deliver a product or service, from request to delivery. It shows process times, waiting times and inventory so you can see how much of the lead time actually adds value. Teams draw a current state map, design a future state and then plan the kaizen events to get there.
Variation
Variation is the natural difference between one result and the next in any process. Common cause variation is the normal background noise of a process, while special cause variation comes from a specific, unusual event. Six Sigma aims to reduce variation so customers get a consistent result.
Visual Management
Visual management means making the status of work, standards and problems obvious at a glance, through boards, floor markings, color codes and signals. When anyone can see whether things are on track, problems get raised and solved faster. It supports huddles, leader standard work and 5S.
VOC (Voice of the Customer)
Voice of the customer is the process of gathering and understanding what customers need, expect and complain about. Sources include interviews, surveys, complaint data and direct observation. VOC is translated into measurable CTQs that guide a project.
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White Belt
A Lean Six Sigma White Belt is an introduction to the basic ideas and vocabulary of Lean and Six Sigma. It helps everyone in an organization understand improvement work and take part in projects. The Belts build on each other, so White Belt is the starting point. Our White Belt is available self-paced.
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Yellow Belt
A Lean Six Sigma Yellow Belt understands the DMAIC roadmap and core tools well enough to be a strong project team member and to lead small improvements in their own area. The Belts build on each other, so Yellow Belt builds on White Belt and leads to Green Belt. Our Yellow Belt is available self-paced as well as live.
Yokoten
Yokoten means sharing a proven improvement across other areas, lines or sites so that everyone benefits. It is more than copying; teams adapt the idea to fit their own conditions. Yokoten turns one team's win into an organization-wide gain.
Training a whole team? We bring any program to your site or online for your group. See group training.
