5 Whys
Root cause analysis
A technique of not stopping at the symptom of a problem but asking “why?” repeatedly to get down to the root cause. If the solution is applied to the root cause, the problem does not recur.
Lean Glossary
Plain-language explanations of 74 terms we use in the world of lean manufacturing, kaizen, TPM, OPEX and shop floor management. Written from the shop floor, from our consulting experience.
0-9
5S
Japanese: Seiri, Seiton, Seiso, Seiketsu, Shitsuke
A five-step method aimed at keeping the workplace organized, clean and standardized: sort, set in order, shine, standardize, sustain discipline. It is the first and most visible step of lean management.
Lean production consulting →7 Muda (Seven Wastes)
Japanese: muda = waste
Seven types of loss the customer does not want to pay for: overproduction, waiting, unnecessary transport, over-processing, inventory, unnecessary motion and defects. Many sources add unused employee talent as an eighth.
What is lean production? →A
A3 Report
Problem-solving document
A thinking and reporting method that fits the problem, root cause, countermeasures and follow-up plan onto a single A3 sheet. It follows PDCA logic and brings the team to a common language.
Andon
Japanese: lamp, lantern
A visual alert system that signals an abnormality on the line with light or sound. The problem becomes visible instantly and the team responds quickly.
What is visual management? →Asakai
Japanese: morning meeting
A morning meeting where the previous day's quality, delivery and production problems are discussed briefly and in a focused way on the floor. Problem owners and actions become visible.
Shop floor management and development system →Autonomous Maintenance (Jishu Hozen)
TPM pillar
The operator taking on basic maintenance tasks such as cleaning, inspecting and lubricating their own machine. It catches failures early.
TPM consulting →B
Batch Production
Production method
Processing products in large batches and transferring them to the next station all at once. Because it increases inventory and waiting time, the lean approach aims for small batches and one-piece flow.
Bottleneck
Flow constraint
The slowest link in the process. This link determines the output of the whole line; improvement should be made here first.
C
Catchball
Hoshin Kanri practice
Goals being discussed back and forth between upper and lower levels “like throwing a ball” and becoming clear through agreement. It creates ownership instead of imposing targets.
Hoshin Kanri consulting →Cost Reduction
Management objective
The effort to offer the same value at lower cost by removing waste and non-value-adding activity. From a lean perspective, it is done without sacrificing quality or flow.
What is cost reduction? →Cycle Time
Measurement
The time an operation or station takes to complete one unit from start to finish. By comparing it with takt time, you can tell whether the line meets demand.
D
Digital Transformation
Technology and process
Redesigning processes, data and decision making with digital tools. Digitalizing a process without a lean foundation only speeds up waste.
Digital transformation consulting →Dojo
Japanese: training hall
A training area focused on simulation and workshops where employees learn by practicing the work on the floor. It is used to turn knowledge into behavior.
Gemba Technical Training Center →F
FIFO
First In, First Out
“First in, first out.” A flow rule that ensures materials are used in sequence and stock does not age.
First Time Quality (FTQ)
Right the first time
The rate at which a product is made right the first time without needing any correction or rework. It is an indicator in which quality and efficiency are tracked together.
G
Gemba
Japanese: the real place
The place where the work happens and value is created; in production, the floor, workshop and line. Lean management advocates making decisions by observing in the gemba, not in the office.
Shop floor management →Gemba Walk
Floor walk
Managers going to the floor to observe the process, people and problems on the spot and talk with employees. The aim is not to inspect but to understand and support.
Shop floor management and development system →Genchi Genbutsu
Japanese: go and see for yourself
The principle of understanding a problem with real data at the place where it happened, not at a desk. It is one of the core behaviors of the Toyota Production System.
H
Hansei
Japanese: reflection
The habit of honestly evaluating mistakes at the end of a task and creating a culture of learning. It does not look for someone to blame and feeds continuous improvement.
Heijunka
Japanese: leveling
An approach that smooths fluctuations by spreading production volume and product mix evenly over time. It reduces inventory and overtime.
Hoshin Kanri
Strategy deployment
A policy management method that links company strategy step by step to annual goals and actions on the floor. It ensures everyone works toward the same goal.
Hoshin Kanri consulting →I
Inventory
One of the seven wastes
The quantity of unsold raw material, work in process and finished goods. Inventory hides problems, which is why the lean approach aims to reduce it.
Ishikawa (Fishbone) Diagram
Cause-and-effect analysis
A visual analysis tool that groups the possible causes of a problem under the headings of people, machine, method, material, measurement and environment.
J
Jidoka
Japanese: automation with a human touch
The principle of stopping the process when a machine or operator notices a defect, preventing the defective product from moving on. It assures quality at the source.
Just in Time (JIT)
Just-in-time production
The principle of producing the needed product, in the needed quantity, at the needed time. It reduces inventory and waiting time and makes the flow responsive to problems.
What is just-in-time production? →K
Kaizen
Japanese: continuous improvement
The philosophy of making small and continuous improvements with everyone's participation. Instead of big breakthroughs, it aims to be a little better every day.
What is Kaizen? →Kaizen Event (Kaizen Blitz)
Focused improvement effort
An intensive effort in which a cross-functional team analyzes and improves a specific process on the floor over a few days. Results are seen quickly.
Kanban
Japanese: card, signal
A pull system tool that communicates a material or production need by card, bin or signal. It prevents overproduction and limits inventory.
What is Kanban? →Kata (Toyota Kata)
Habit, routine
A learning and coaching method that makes it routine to set a target condition and overcome obstacles with small experiments.
KPI
Key performance indicator
A measure showing the status of a process or team against its goal. In lean management, KPIs are tracked daily on floor boards.
Shop floor management →L
Layout Planning
Factory design
The work of designing the flow of machines, materials and people to minimize waste. It is a core step in new factory setups.
Layout planning consulting →Lead Time
Measurement
The total time from receiving an order to delivering the product to the customer. It includes waiting times; it is a core goal of lean practices.
Leader Standard Work
Gemba leadership
Standardizing the verification, observation and support activities managers will perform regularly during the day. It makes management on the floor sustainable.
Leadership development program →Lean Leadership
Leadership approach
A manager showing behaviors that learn on the floor, coach and sustain a culture of improvement.
Lean leadership competencies →Lean Production
Production approach
A production and management approach that aims to continuously reduce waste while increasing customer value. Its source is the Toyota Production System.
What is lean production? →Lean Transformation
Change approach
A company permanently changing its processes, culture and management system according to lean principles. It is more about behavior change than tool use.
What is lean transformation? →Line Balancing
Flow design
Distributing work content across stations so that each one's time is close to takt time. Waiting and overload are reduced.
M
Mizusumashi
Japanese: water spider
A material handler role that circulates along a set route on the line, feeding materials to line sides and collecting empty containers. The operator does not search for materials and focuses on the work.
MTBF / MTTR
Maintenance indicators
MTBF shows the average time between two failures (reliability); MTTR shows the average repair time of a failure.
What is OEE? →Muda
Japanese: waste
Any activity that adds no value. The lean approach aims to make muda visible and remove it.
What is lean production? →Mura
Japanese: unevenness
Fluctuation in workload, demand and output. Mura creates waiting in one place and overload in another.
Muri
Japanese: overburden
Straining people or machines beyond their capacity. It leads to quality problems, breakdowns and workplace accidents.
N
Nemawashi
Japanese: preparing the roots
The practice of building consensus by talking with the relevant people one by one before a decision is made. Resistance during implementation is reduced.
O
Obeya
Japanese: big room
A shared management room where all indicators related to a project or strategy are posted on the walls and the team meets periodically.
OEE
Overall Equipment Effectiveness
An equipment effectiveness indicator found by multiplying availability, performance and quality rates. It shows how efficiently the machine runs during planned time.
What is OEE? →One-Piece Flow
Flow method
Products flowing one by one between stations without waiting. It makes inventory and defects quickly visible.
OPEX
Operational Excellence
An approach that takes processes, people and culture to peak performance through continuous improvement. It brings lean, TPM and quality under one roof.
What is OPEX? →P
Pareto Analysis
80/20 principle
An analysis showing that most problems come from a small number of causes. Improvement effort is directed to where it is most effective.
PDCA
Plan-Do-Check-Act
The basic cycle of continuous improvement: plan, do, check the result, standardize or act again.
Poka-Yoke
Japanese: mistake-proofing
Simple designs and devices that make an error impossible or catch it the moment it is made. They assure quality through design, not inspection.
Preventive Maintenance
Maintenance strategy
Maintenance carried out at planned intervals before a failure occurs. It reduces unplanned stoppages and extends equipment life.
TPM consulting →Productivity
Efficiency measure
The ratio of output achieved to input used. The lean approach raises productivity by reducing waste, not by making employees go faster.
Productivity improvement consulting →Pull System
Flow management
Starting production based on actual customer demand or the next station's need rather than pushing it by forecast. Kanban and supermarkets are tools of this system.
What is Kanban? →R
Root Cause Analysis
Problem-solving method
A systematic investigation aimed at finding the real source of a problem, not the symptom. 5 Whys, Ishikawa and Pareto are commonly used tools.
S
Seiri / Seiton / Seiso / Seiketsu / Shitsuke
5S steps
Sorting, setting in order, shining, standardizing and discipline, respectively. Each step is the foundation of the next.
Lean production consulting →Sensei
Japanese: teacher, master
An experienced person who teaches and coaches lean practice on the floor. While passing on knowledge, they let the team find its own solution.
Shop Floor Management (SFM)
Floor management
Managing the production floor through daily goal, deviation and action tracking. It is built on visual boards, short meetings and gemba walks.
What is Shop Floor Management? →SIPOC
Process map
A map showing supplier, input, process, output and customer in a single high-level frame. It clarifies the boundaries of the process.
Six Sigma
Quality method
A method that aims to minimize defects by statistically reducing variation in processes. Combined with lean, it is used under the name “Lean Six Sigma.”
SMED
Single Minute Exchange of Die
A method for shortening setup and die-change times. By separating internal and external preparation, it reduces machine downtime.
What is SMED? →SQCDM
Floor board headings
A performance board structure tracked daily on the floor under the headings of safety, quality, cost, delivery and morale/people.
Shop floor management →Standardized Work
Lean standard
Defining the best known method of a job with time, sequence and stock rules. Improvement is built on top of the standard.
Supermarket
Material management
A controlled material area held at a set place at the line side and replenished with a pull signal. It works together with kanban.
What is Kanban? →T
Takt Time
German: rhythm
The time in which a product must be produced to meet customer demand. It is found by dividing available working time by daily demand.
TPM
Total Productive Maintenance
A maintenance and efficiency system in which operators, maintenance and management work together to bring equipment losses close to zero.
TPM consulting →TPS (Toyota Production System)
Origin of lean
Toyota's management system, the origin of lean production, built on the pillars of JIT and Jidoka.
What is lean production? →U
U-Cell
Cellular layout
A production cell where machines are arranged in a U shape and the operator works close to both the entry and the exit. It provides flexible workload distribution.
Layout planning →V
Value Stream Mapping (VSM)
Value Stream Mapping
An analysis tool that shows all the steps, times and inventories a product goes through from order to delivery on a single map. It reveals where waste accumulates.
What is VSM? →Value-Adding / Non-Value-Adding Activity
Core concept
Steps the customer is willing to pay for in a product or service are value-adding activity. Every other step, even if necessary, is a candidate for waste and efforts are made to reduce it.
Visual Management
Lean tool
Showing goals, status and deviations through boards, colors and signs so everyone understands at a glance. By making problems visible, it enables fast decisions.
What is visual management? →W
WIP (Work in Process)
Flow measure
The quantity of product waiting to be processed or being processed on the line. High WIP means long lead time and hidden problems.
Y
Yamazumi
Japanese: stacking
A chart showing the workloads of stations as stacked columns. It is used for line balancing and comparison with takt.
Gemba Digital tools →Yokoten
Japanese: horizontal spreading
The systematic spreading of an improvement that worked in one unit to other units. It carries learning across the company.
No terms match your search.
Let's turn the terms into practice on your floor
To bring the concepts in the glossary to life in your factory, train your team, or assess your current state together, get in touch with us.
Get in TouchBlog Posts
Lean Glossary
Plain-language explanations of 74 terms we use in the world of lean manufacturing, kaizen, TPM, OPEX and shop floor management. Written from the shop floor, from our consulting experience.
0-9
5 Whys
Root cause analysis
A technique of not stopping at the symptom of a problem but asking “why?” repeatedly to get down to the root cause. If the solution is applied to the root cause, the problem does not recur.
5S
Japanese: Seiri, Seiton, Seiso, Seiketsu, Shitsuke
A five-step method aimed at keeping the workplace organized, clean and standardized: sort, set in order, shine, standardize, sustain discipline. It is the first and most visible step of lean management.
Lean production consulting →7 Muda (Seven Wastes)
Japanese: muda = waste
Seven types of loss the customer does not want to pay for: overproduction, waiting, unnecessary transport, over-processing, inventory, unnecessary motion and defects. Many sources add unused employee talent as an eighth.
What is lean production? →A
A3 Report
Problem-solving document
A thinking and reporting method that fits the problem, root cause, countermeasures and follow-up plan onto a single A3 sheet. It follows PDCA logic and brings the team to a common language.
Andon
Japanese: lamp, lantern
A visual alert system that signals an abnormality on the line with light or sound. The problem becomes visible instantly and the team responds quickly.
What is visual management? →Asakai
Japanese: morning meeting
A morning meeting where the previous day's quality, delivery and production problems are discussed briefly and in a focused way on the floor. Problem owners and actions become visible.
Shop floor management and development system →Autonomous Maintenance (Jishu Hozen)
TPM pillar
The operator taking on basic maintenance tasks such as cleaning, inspecting and lubricating their own machine. It catches failures early.
TPM consulting →B
Batch Production
Production method
Processing products in large batches and transferring them to the next station all at once. Because it increases inventory and waiting time, the lean approach aims for small batches and one-piece flow.
Bottleneck
Flow constraint
The slowest link in the process. This link determines the output of the whole line; improvement should be made here first.
C
Catchball
Hoshin Kanri practice
Goals being discussed back and forth between upper and lower levels “like throwing a ball” and becoming clear through agreement. It creates ownership instead of imposing targets.
Hoshin Kanri consulting →Cost Reduction
Management objective
The effort to offer the same value at lower cost by removing waste and non-value-adding activity. From a lean perspective, it is done without sacrificing quality or flow.
What is cost reduction? →Cycle Time
Measurement
The time an operation or station takes to complete one unit from start to finish. By comparing it with takt time, you can tell whether the line meets demand.
D
Digital Transformation
Technology and process
Redesigning processes, data and decision making with digital tools. Digitalizing a process without a lean foundation only speeds up waste.
Digital transformation consulting →Dojo
Japanese: training hall
A training area focused on simulation and workshops where employees learn by practicing the work on the floor. It is used to turn knowledge into behavior.
Gemba Technical Training Center →F
FIFO
First In, First Out
“First in, first out.” A flow rule that ensures materials are used in sequence and stock does not age.
First Time Quality (FTQ)
Right the first time
The rate at which a product is made right the first time without needing any correction or rework. It is an indicator in which quality and efficiency are tracked together.
G
Gemba
Japanese: the real place
The place where the work happens and value is created; in production, the floor, workshop and line. Lean management advocates making decisions by observing in the gemba, not in the office.
Shop floor management →Gemba Walk
Floor walk
Managers going to the floor to observe the process, people and problems on the spot and talk with employees. The aim is not to inspect but to understand and support.
Shop floor management and development system →Genchi Genbutsu
Japanese: go and see for yourself
The principle of understanding a problem with real data at the place where it happened, not at a desk. It is one of the core behaviors of the Toyota Production System.
H
Hansei
Japanese: reflection
The habit of honestly evaluating mistakes at the end of a task and creating a culture of learning. It does not look for someone to blame and feeds continuous improvement.
Heijunka
Japanese: leveling
An approach that smooths fluctuations by spreading production volume and product mix evenly over time. It reduces inventory and overtime.
Hoshin Kanri
Strategy deployment
A policy management method that links company strategy step by step to annual goals and actions on the floor. It ensures everyone works toward the same goal.
Hoshin Kanri consulting →I
Inventory
One of the seven wastes
The quantity of unsold raw material, work in process and finished goods. Inventory hides problems, which is why the lean approach aims to reduce it.
Ishikawa (Fishbone) Diagram
Cause-and-effect analysis
A visual analysis tool that groups the possible causes of a problem under the headings of people, machine, method, material, measurement and environment.
J
Jidoka
Japanese: automation with a human touch
The principle of stopping the process when a machine or operator notices a defect, preventing the defective product from moving on. It assures quality at the source.
Just in Time (JIT)
Just-in-time production
The principle of producing the needed product, in the needed quantity, at the needed time. It reduces inventory and waiting time and makes the flow responsive to problems.
What is just-in-time production? →K
Kaizen
Japanese: continuous improvement
The philosophy of making small and continuous improvements with everyone's participation. Instead of big breakthroughs, it aims to be a little better every day.
What is Kaizen? →Kaizen Event (Kaizen Blitz)
Focused improvement effort
An intensive effort in which a cross-functional team analyzes and improves a specific process on the floor over a few days. Results are seen quickly.
Kanban
Japanese: card, signal
A pull system tool that communicates a material or production need by card, bin or signal. It prevents overproduction and limits inventory.
What is Kanban? →Kata (Toyota Kata)
Habit, routine
A learning and coaching method that makes it routine to set a target condition and overcome obstacles with small experiments.
KPI
Key performance indicator
A measure showing the status of a process or team against its goal. In lean management, KPIs are tracked daily on floor boards.
Shop floor management →L
Layout Planning
Factory design
The work of designing the flow of machines, materials and people to minimize waste. It is a core step in new factory setups.
Layout planning consulting →Lead Time
Measurement
The total time from receiving an order to delivering the product to the customer. It includes waiting times; it is a core goal of lean practices.
Leader Standard Work
Gemba leadership
Standardizing the verification, observation and support activities managers will perform regularly during the day. It makes management on the floor sustainable.
Leadership development program →Lean Leadership
Leadership approach
A manager showing behaviors that learn on the floor, coach and sustain a culture of improvement.
Lean leadership competencies →Lean Production
Production approach
A production and management approach that aims to continuously reduce waste while increasing customer value. Its source is the Toyota Production System.
What is lean production? →Lean Transformation
Change approach
A company permanently changing its processes, culture and management system according to lean principles. It is more about behavior change than tool use.
What is lean transformation? →Line Balancing
Flow design
Distributing work content across stations so that each one's time is close to takt time. Waiting and overload are reduced.
M
Mizusumashi
Japanese: water spider
A material handler role that circulates along a set route on the line, feeding materials to line sides and collecting empty containers. The operator does not search for materials and focuses on the work.
MTBF / MTTR
Maintenance indicators
MTBF shows the average time between two failures (reliability); MTTR shows the average repair time of a failure.
What is OEE? →Muda
Japanese: waste
Any activity that adds no value. The lean approach aims to make muda visible and remove it.
What is lean production? →Mura
Japanese: unevenness
Fluctuation in workload, demand and output. Mura creates waiting in one place and overload in another.
Muri
Japanese: overburden
Straining people or machines beyond their capacity. It leads to quality problems, breakdowns and workplace accidents.
N
Nemawashi
Japanese: preparing the roots
The practice of building consensus by talking with the relevant people one by one before a decision is made. Resistance during implementation is reduced.
O
Obeya
Japanese: big room
A shared management room where all indicators related to a project or strategy are posted on the walls and the team meets periodically.
OEE
Overall Equipment Effectiveness
An equipment effectiveness indicator found by multiplying availability, performance and quality rates. It shows how efficiently the machine runs during planned time.
What is OEE? →One-Piece Flow
Flow method
Products flowing one by one between stations without waiting. It makes inventory and defects quickly visible.
OPEX
Operational Excellence
An approach that takes processes, people and culture to peak performance through continuous improvement. It brings lean, TPM and quality under one roof.
What is OPEX? →P
Pareto Analysis
80/20 principle
An analysis showing that most problems come from a small number of causes. Improvement effort is directed to where it is most effective.
PDCA
Plan-Do-Check-Act
The basic cycle of continuous improvement: plan, do, check the result, standardize or act again.
Poka-Yoke
Japanese: mistake-proofing
Simple designs and devices that make an error impossible or catch it the moment it is made. They assure quality through design, not inspection.
Preventive Maintenance
Maintenance strategy
Maintenance carried out at planned intervals before a failure occurs. It reduces unplanned stoppages and extends equipment life.
TPM consulting →Productivity
Efficiency measure
The ratio of output achieved to input used. The lean approach raises productivity by reducing waste, not by making employees go faster.
Productivity improvement consulting →Pull System
Flow management
Starting production based on actual customer demand or the next station's need rather than pushing it by forecast. Kanban and supermarkets are tools of this system.
What is Kanban? →R
Root Cause Analysis
Problem-solving method
A systematic investigation aimed at finding the real source of a problem, not the symptom. 5 Whys, Ishikawa and Pareto are commonly used tools.
S
Seiri / Seiton / Seiso / Seiketsu / Shitsuke
5S steps
Sorting, setting in order, shining, standardizing and discipline, respectively. Each step is the foundation of the next.
Lean production consulting →Sensei
Japanese: teacher, master
An experienced person who teaches and coaches lean practice on the floor. While passing on knowledge, they let the team find its own solution.
Shop Floor Management (SFM)
Floor management
Managing the production floor through daily goal, deviation and action tracking. It is built on visual boards, short meetings and gemba walks.
What is Shop Floor Management? →SIPOC
Process map
A map showing supplier, input, process, output and customer in a single high-level frame. It clarifies the boundaries of the process.
Six Sigma
Quality method
A method that aims to minimize defects by statistically reducing variation in processes. Combined with lean, it is used under the name “Lean Six Sigma.”
SMED
Single Minute Exchange of Die
A method for shortening setup and die-change times. By separating internal and external preparation, it reduces machine downtime.
What is SMED? →SQCDM
Floor board headings
A performance board structure tracked daily on the floor under the headings of safety, quality, cost, delivery and morale/people.
Shop floor management →Standardized Work
Lean standard
Defining the best known method of a job with time, sequence and stock rules. Improvement is built on top of the standard.
Supermarket
Material management
A controlled material area held at a set place at the line side and replenished with a pull signal. It works together with kanban.
What is Kanban? →T
Takt Time
German: rhythm
The time in which a product must be produced to meet customer demand. It is found by dividing available working time by daily demand.
TPM
Total Productive Maintenance
A maintenance and efficiency system in which operators, maintenance and management work together to bring equipment losses close to zero.
TPM consulting →TPS (Toyota Production System)
Origin of lean
Toyota's management system, the origin of lean production, built on the pillars of JIT and Jidoka.
What is lean production? →U
U-Cell
Cellular layout
A production cell where machines are arranged in a U shape and the operator works close to both the entry and the exit. It provides flexible workload distribution.
Layout planning →V
Value Stream Mapping (VSM)
Value Stream Mapping
An analysis tool that shows all the steps, times and inventories a product goes through from order to delivery on a single map. It reveals where waste accumulates.
What is VSM? →Value-Adding / Non-Value-Adding Activity
Core concept
Steps the customer is willing to pay for in a product or service are value-adding activity. Every other step, even if necessary, is a candidate for waste and efforts are made to reduce it.
Visual Management
Lean tool
Showing goals, status and deviations through boards, colors and signs so everyone understands at a glance. By making problems visible, it enables fast decisions.
What is visual management? →W
WIP (Work in Process)
Flow measure
The quantity of product waiting to be processed or being processed on the line. High WIP means long lead time and hidden problems.
Y
Yamazumi
Japanese: stacking
A chart showing the workloads of stations as stacked columns. It is used for line balancing and comparison with takt.
Gemba Digital tools →Yokoten
Japanese: horizontal spreading
The systematic spreading of an improvement that worked in one unit to other units. It carries learning across the company.
No terms match your search.
Let's turn the terms into practice on your floor
To bring the concepts in the glossary to life in your factory, train your team, or assess your current state together, get in touch with us.
Get in TouchBlog Posts
LEAN GLOSSARY
The Terms We Use on the Shop Floor, in Brief
Plain-language English equivalents of lean manufacturing terms of Japanese origin. Each term links to the relevant articles.
All terms →
Andon
A visual/audible alert system that makes a problem on the line instantly visible and calls for help.
Heijunka
A planning approach that balances production volume and product mix over time.
Jidoka
Automation with a human touch that stops production when an abnormality occurs and prevents defective products from moving on.
Kaizen
Small, continuous, shop-floor-based improvements made with everyone's participation.
Kanban
A signal card that triggers production and material replenishment in a pull system.
Poka-yoke
A simple error-proofing device that prevents a mistake before it occurs or notices it immediately.
SMED
A quick changeover method aimed at reducing die and model changeover times to single-digit minutes.
Yamazumi
A stacked bar chart comparing station workloads with cycle time; the basic tool of line balancing.