Glossary of Maintenance Terms and Definitions

Glossary of Maintenance Terms and Definitions


If you want to succeed in maintenance, it helps if you can talk the talk. But, like many specialized fields, maintenance has its own lingo – terms and phrases, each with a specific meaning relating to the work that goes on in a maintenance department.

From asset tracking to wrench time, we will provide you with explanations and context for them all.  The only thing left for you to do is walk the walk.



Any physical item such as a piece of equipment or property that is used in a facility’s operations. Assets provide some kind of benefit to the business such as greater efficiency or product quality, reduced labor costs, or automation.

Asset Tracking

The process of tracking the location, condition, and status of physical assets used in your organization’s operations. Many different strategies, resources, and best practices can help an organization perform asset tracking effectively.

Asset Utilization

A ratio that measures how efficiently an organization uses its assets to make money and turn a profit. Implementing a measurement of asset utilization can help organizations ensure the greatest return on their investment in asset acquisition, use, and maintenance.

Autonomous Maintenance

A maintenance strategy that involves shifting some maintenance tasks to the machine operators themselves. Autonomous maintenance can reduce reliance on the dedicated maintenance staff, freeing them up for more specialized maintenance and repair work.

Asset Availability

A measurement of how likely an asset is to be in operable condition at any given time. Asset availability is a part of the Reliability, Availability, and Maintainability analysis which can be used to reduce waste and improve the productivity of an asset.


A printed series of parallel bars or lines and spaces of varying widths that is machine readable. If used with a CMMS by your maintenance team, barcodes can be scanned to help identify assets and quickly provide maintenance professionals with helpful information on that asset. Barcode asset tracking provides many benefits and efficiencies for maintenance programs.

Breakdown Maintenance

Maintenance performed on an asset that has experienced failure, with the goal of restoring it to an optimal operating condition. While some breakdown maintenance is inevitable, managing it effectively can help reduce downtime and other losses.


A software solution that helps businesses manage, automate, and streamline all of their maintenance operations. An acronym for Computerized Maintenance Management System, a CMMS is a centralized web and mobile software that can hold all maintenance information allowing teams to manage all maintenance work in one single spot.

Computer-Aided Facility Management (CAFM)

Technology that combines business administration, behavioral science, architecture, and engineering concepts in order to improve organizational functionality.  CAFM systems help facility managers track, manage, and report on day-to-day business operations at their facility.

Condition Based Maintenance

A maintenance methodology in which maintenance operations are performed depending on the current condition of your assets. One maintenance strategy of many, condition based maintenance uses condition monitoring data to trigger proactive maintenance and address deterioration early.

Condition Monitoring

The process of monitoring an asset’s condition in order to identify potential problems or maintenance needs. This may include vibration analysis, ultrasonic testing, infrared testing, and other techniques.

Continuous Manufacturing

The process of manufacturing large quantities of products with few variations. Also referred to as continuous production, it relies on highly standardized processes, process sequences, tools, and equipment, that flow continually, without pause.

Corrective Maintenance

Any maintenance task that is performed in order to restore equipment, machinery, or systems to proper working order. When balanced with proactive maintenance, corrective maintenance is an unavoidable part of any maintenance program.

Criticality Analysis

A structured and systematic method of assessing the risk an asset failure would pose to a business. In the implementation of targeted plant maintenance strategies, criticality analysis is used to rank the criticality of assets relative to one another in order to prioritize maintenance activities.

Deferred Maintenance

The practice of postponing maintenance work to a later date due to a lack of necessary resources. The most efficient maintenance programs will have a defined process for handling deferred maintenance, anticipating inevitable resource limitations.


A reduction in the value of an asset over time, due in part to wear and tear. Estimating equipment depreciation can help you determine whether it is more cost-effective to replace an asset or continue repairing it.

Destructive Testing

A test method conducted to find the exact point of failure of materials, components, or machines by applying stress that eventually deforms or destroys the material. Destructive testing is generally conducted before a component enters mass production.


A step-by-step way to identify all possible failures in a certain design and study their effects on production. Typically used in conjunction with PFMEA, DFMEA or Design Failure Modes and Effects Analysis is a tool to put new designs and processes under scrutiny, ensuring they are built to avoid foreseeable failures.


A period during which a system is unavailable. Along with the negative impacts on production and revenue, downtime can disrupt relationships and contracts with partnering companies due to the obstructed flow of input and output.

Enterprise Asset Management

A set of processes and tools that allow companies to track and manage their physical assets (machines, equipment, buildings, and vehicles) throughout their lifecycle – from procurement to disposal. Investing in EAM provides a reliable big-picture perspective on your assets across locations, departments, and facilities, whether those assets are fixed or movable.

Maintenance Acronym Guide

Confused by PMs, MTTR, and DFMEA? This maintenance acronym guide will have you talking the talk in no time.


Failure Analysis

The process of collecting and analyzing failure data, usually to identify the root cause of an asset malfunction/breakdown after it has occurred. The goal of failure analysis is to improve asset reliability.

Failure Mode

The cause of a failure, or one possible way a system may fail.  Failure modes are the starting data point for Failure Mode and Effects Analyses, a common risk mitigation tool in production and manufacturing.

Fault Detection

The process of discovering the presence of a fault in any equipment before it manifests itself in the form of a breakdown. Fault detection is a key part of understanding equipment failure.

Fault Tolerance

The capability of any system or equipment to sustain operations during the presence of a fault. Systems and equipment with high fault tolerance, depending upon the adopted fault tolerance mechanism, are able to completely or partially sustain their operation upon the occurrence of a fault.

Fault Tree Analysis

A tool to analyze the potential for system or machine failure by graphically and mathematically representing the system itself. A top-down approach to risk mitigation, fault tree analysis first identifies the root causes of a potential failure and ends with identification of steps to minimize or mitigate the risk of that failure.

Field Failure Analysis

The analysis of failed components that have been returned to suppliers, particularly those with no-fault found reports. Involving the entire supply chain, field failure analysis provides discrete steps, defined procedures, and a clear allocation of responsibilities.

Fixed Asset Management

The process of tracking, managing, monitoring, and maintaining assets with a long life cycle. Various software tools are used to streamline fixed asset management and make the most of the most costly assets in an organization’s operation.

Fixed Asset Turnover Ratio (FATR)

A calculation that quantifies how efficiently a company is making money with its machines and equipment. Often considered together with Return on Fixed Assets (RoFa), Fixed Asset Turnover Ratio (FATR) is a ratio of net sales to fixed assets.


An analysis method that reveals the specific ways a process could fail and the ways those failures could impact the rest of the system. By searching for weak points in materials, manufacturing processes, and subsystems, FMEA helps minimize impacts on overall processes and operations.


An analysis similar to FMEA, that also includes criticality analysis. An acronym for failure mode effects and criticality analysis, FMECA explores potential failures and their effects, but also uses a criticality analysis component to help you rank failure modes, making prioritization easier.

Idle Time

A period of time in which an asset (machine or employee) is ready and available, but not being productive. Idle time points to the gap between your existing output and your theoretically maximal productivity level.


An acronym for Industrial Internet of Things, referring to network-connected devices that are used specifically for industrial purposes. Given the mission-criticality of these systems, IIoT maintenance is essential for ensuring their reliability, robustness, size, and security.

Industrial Maintenance

The processes and systems used in an industrial setting to reduce breakdowns, increase uptime, and generally ensure that assets are kept in good working condition. Monitoring and maintaining production equipment at an industrial scale utilizes specific resources and and involves a long maintenance tools list.

Key Performance Indicators

A performance measurement that focuses maintenance work on desired organizational outcomes. A maintenance KPI is a quantifiable value that shows how effectively an organization is progressing toward key maintenance objectives over time.

Lean Maintenance

A strategy for reducing waste and inefficiency in the management of physical assets. Lean maintenance applies lean methodology – typically used to optimize production processes – to asset maintenance and repairs.

Lean Manufacturing

A philosophy of production focused on removing anything from a production process that does not add value to the finished product and the customer. Lean manufacturing allows organizations to generate maximum value for the customer while minimizing costs and overheads.

Lockout Tagout (LOTO)

A set of safety protocols and checklists that protect workers from injury by a sudden machine start-up or by releasing hazardous energy while performing maintenance activities. To ensure compliance and provide sufficient safety assurances for your team, it is essential to ensure that strictly followed LOTO procedure is part of your LOTO program.

Machine Efficiency

A measurement of the degree to which a machine is achieving its theoretical maximum production or output. The efficiency of a machine is calculated by comparing the output to a specific input which allows you to determine efficiency from many different perspectives.

Machine Monitoring

A systematic process of recording condition data from any machine in order to assess its performance and determine its health. Machine monitoring provides a reliable, consistent, and high-quality stream of data to operators, maintainers, and engineers/designers that can be used to improve maintenance and operations.


A concept used by equipment manufacturers, operators, and asset managers that represents the ease of maintaining a particular asset. Maintainability is a part of the Reliability, Availability, and Maintainability (RAM) analysis which can be used to reduce waste and improve the productivity of an asset.


The process of maintaining or preserving a physical asset that is essential to a business’s operations in order to keep that business running. Most businesses use a combination of 3 types of maintenance, and organize that work according to a specific maintenance strategy   that suits their business best.

Maintenance Checklist

A tool used by maintenance workers to document equipment maintenance activities and ensure necessary steps are taken consistently. The use of a preventive maintenance checklist has many benefits including improved safety and adherence to standard operating procedures.

Maintenance Costs

All expenses that are the result of efforts to keep physical assets in optimal working condition. A thorough understanding and awareness of each maintenance cost is essential for running an efficient maintenance program.

Maintenance Policy

A document produced, owned, and managed by senior management intended to establish the expectations of a maintenance department. The contents of a maintenance policy must support and enable the mission, values, and business objectives.

Maintenance Repair and Operations

A phrase that refers to the equipment, tools, and activities a maintenance team performs to keep your facility (and the equipment inside it) in good operating condition. Sometimes referred to as Maintenance Repair and Overhaul, a well-run MRO program can offer significant benefits to an organization’s productivity.

Maintenance Report

A document that contains specific information or summaries of your past maintenance actions and their impact on cost, assets, and business performance. In general, a maintenance report is used to track KPIs and performance indicators which demonstrate the maintenance department’s contribution to the organization’s success and productivity.

Maintenance Strategy

An intentional plan for addressing an organization’s maintenance needs involving the identification of maintenance needs, and method of execution, evaluation, and documentation. There are many different approaches to organizing maintenance work, and each organization must choose the right maintenance strategy for its unique needs.

Mobile Maintenance

A maintenance solution that you can install on your mobile device as an app. A distinct mobile application — as opposed to a maintenance management system that is accessible from any browser — is essential for ensuring your team can use the mobile maintenance software accurately and regularly.

Mean Time Between Failures (MTBF)

The amount of time required to repair a system and restore it to full functionality. MTTF, MTTR, and MTBF are the three key failure metrics maintenance departments use to better understand equipment maintenance and lifecycle.

Mean Time to Failure (MTTF)

The length of time an item is expected to last in operation until it needs to be replaced. MTTF, MTTR, and MTBF are the three key failure metrics maintenance departments use to better understand equipment maintenance and lifecycle.

Mean Time To Repair (MTTR)

The amount of time required to repair a system and restore it to full functionality (also referred to as Mean Time To Recover). MTTFMTTR, and MTBF are the three key failure metrics maintenance departments use to better understand equipment maintenance and lifecycle.

The Essential Guide to CMMS

The Essential Guide to CMMS


Non-Destructive Testing

Testing methods that do not compromise the structural integrity of the parts being tested. Non destructive testing (NDT) employs various inspection techniques to evaluate components, individually or collectively.

Operating Hours

A unit of time that is used to measure active operating time of a machine or system.  The measurement of operating hours is used for various efficiency metrics such as Overall Equipment Effectiveness and failure metrics like MTTF.

Original Equipment Manufacturer (OEM)

A company whose products are used as components in the creation of a finished product by another company. The OEM has a significant impact on the long-term quality, productivity, and ROI of a procured asset, and is, therefore, an essential consideration and resource for any maintenance department.

Overall Equipment Effectiveness

A key performance indicator (maintenance KPI) that compares your equipment’s ideal performance to its real performance. OEE is a quantifiable (i.e., numerical) way to find out how well your equipment, people, and processes do their job.

P-F Curve (P-F Interval)

A graphical visualization of the degradation of a piece of equipment over time. The purpose of the PF curve is to determine the most effective times to perform maintenance work that minimizes failures and work disruptions and maximizes productivity.


A step-by-step way to identify all possible failures in a certain process and study their effects on production. Typically used in conjunction with DFMEA, PFMEA or Process Failure Modes and Effects Analysis is a tool to put new designs and processes under scrutiny, ensuring they are built to avoid foreseeable failures.

Planned Downtime

A period of time you reserve for scheduled maintenance and upgrades during which your assets have to be shut down. Planned downtime typically applies to critical assets that are so important to production that you don’t have any other solution than to pause normal production operations to complete the needed maintenance.

Planned Maintenance

A proactive approach to maintenance management in which services are scheduled to take place on a regular basis. As a general rule, the more planned maintenance you perform, the longer your assets will remain operating at peak without failures.

Predictive Maintenance

A method of maintenance that uses condition-monitoring techniques to track the performance of assets during regular operation, detect possible defects, and fix them before the asset failure happens. There are many benefits of predictive maintenance as it provides advanced insight into maintenance needs across an organization.

Prescriptive Maintenance

A method of maintenance that uses condition-monitoring techniques to detect not only when maintenance is needed, but the type of maintenance that needs to be performed as well.   Because it is a highly advanced maintenance technique, prescriptive maintenance requires a fairly evolved maintenance program to be in place already, but also provides many benefits.

Preventive Maintenance

Maintenance work done at regular time frames to fix signs of wear before they lead to breakdowns. Preventive maintenance is sometimes also referred to as preventative maintenance, and is the first step into proactive maintenance.

Proactive Maintenance

Maintenance work that is done in order to prevent a breakdown before it occurs. Instead of treating the symptoms of a failure, the goal of proactive maintenance is to identify the underlying causes of a malfunction or breakdown – and fix or prevent them in advance.

Productive Efficiency

A concept in economics where a system is producing the largest possible output from the available resources. Also referred to as production efficiency, it is when you are using your limited resources to their fullest potential. The maintenance team plays an essential role in working toward productive efficiency by keeping equipment running.

Purchase Order

A commercial document used to control and document the purchasing of products and services from external suppliers.

Reactive Maintenance

The simplest form of physical asset management where operators run assets until they malfunction or completely break down. It is only at the point of breakdown that technicians are called to perform maintenance in a reactive maintenance approach.


In the context of equipment maintenance, a reliability engineering technique that helps a system perform without interruption even when a piece of equipment fails. Equipment redundancy is used across many industries, especially those that have high availability and reliability requirements.


A term used to describe the ability of a component or system to meet certain performance standards over a certain period of time, assuming normal operating conditions. Reliability is a part of the Reliability, Availability, and Maintainability (RAM) analysis which can be used to reduce waste and improve the productivity of an asset.

Reliability Centered Maintenance

A structured process that identifies problems which, when solved, increases the productivity of equipment and assets while reducing maintenance costs. Reliability centered maintenance isn’t necessarily a maintenance method, it’s evaluation criteria to identify which maintenance methods will work best for each piece of machinery.

Reliability Engineering

The systematic application of best engineering practices and techniques to make more reliable products in a cost-effective manner. The reliability engineering methodology can be applied across the product lifecycle: from design and manufacturing to operation and maintenance.


An action we take to restore an asset to proper working conditions. Repair and maintenance are closely linked, but in contrast to maintenance, repair is performed in response to a failure.

Return on Fixed Assets (RoFA)

A calculation that quantifies how much money a company makes in return for its assets. Often considered together with Fixed Asset Turnover Ratio (FATR), RoFA iscalculated by dividing a company’s current operational income by the investment cost of its fixed assets.

Risk-Based Maintenance

A methodology that helps you determine the most economical use of your maintenance resources. The goal of corrective risk-based maintenance is to find the critical/problem assets and dedicate your maintenance resources to them while diverting resources from non-critical assets.

Return on Investment (ROI)

A ratio that demonstrates how much one has gained as a result of a particular investment or expenditure.  Maintenance departments use the concept of ROI to demonstrate how certain investments or expenses lead to greater savings or efficiency such as a CMMS ROI that demonstrates the efficiencies that maintenance management technology can offer.

Root Cause Analysis

The process of finding the underlying cause for an effect. In the context of failure analysis, root cause analysis or RCA is used to find the root cause of frequent machine malfunctions or a significant machine breakdown.

Routine Maintenance

Maintenance activities performed regularly to identify and address issues before they lead to equipment failure. Routine maintenance is an integral part of all preventive maintenance efforts.


A maintenance strategy where maintenance is only performed when equipment has failed.


Schedule Compliance

A maintenance KPI that tracks how many scheduled maintenance tasks have been completed on time compared to the number scheduled. Schedule compliance is important for measuring the effectiveness of a maintenance program.


Devices that are attached to an asset in order to track behavior changes that indicate degradation or the need for maintenance. Technology that enables IIoT sensor setup is essential for using sensors to implement a predictive maintenance program.

Spare Parts

The concept of maintaining an inventory of equipment repair parts in order for them to be immediately available when needed without waiting for a purchase order and delivery, thus minimizing downtime. Spare parts management is the process of ensuring that the right spare parts and resources are available at the right place at the right time.

Standard Operating Procedure

An official document with detailed instructions that outline how to perform a specific task. Standard operating procedures or SOPs are essential for growing businesses that want to maintain consistency and high quality.

Time Study

The act of observing, recording, and rating human work to establish the time it takes to perform specified work under specific conditions at a defined pace. The concept of conducting a time study is critical for improving efficiency on the plant floor.

Total Preventive Maintenance

An organized, standardized, and structured approach to preventive maintenance. Total preventive maintenance, also referred to as total productive maintenance or TPM, trains and empowers machine operators to take on ownership of and basic maintenance responsibilities for the machines they work with the most.


A step-by-step approach to finding the root cause of an issue and deciding the best way to fix it to get it back in operation. Efficient troubleshooting is an essential part of asset management, diagnosis, and repair.

Unplanned Downtime

An unexpected shutdown or failure of equipment or processes. Because of its potential to cause delays and financial losses, it is essential that organizations practice machine downtime tracking to monitor the amount and causes of unplanned downtime.

Unplanned Maintenance

An unexpected issue occurring with no forewarning and, therefore, no ability to moderate the outcome. Unplanned maintenance is an inevitable consequence of equipment operation.


A measure of system reliability, expressed as the percentage of time a machine has been working and available.

Work Order

A task that is scheduled and assigned to a specific person or group of people. A work order is a request that tells your maintenance staff what needs to be done.

Wrench Time

A metric that shows how much time a maintenance technician spends with a tool in their hand, performing actual maintenance work.  Wrench time doesn’t include the time technicians spend getting the right tools and spare parts, reading the work order, traveling to the location where the job is performed, breaks and idle time, giving instructions, and other non-maintenance tasks.

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