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Maintainability is the ease of maintaining or providing maintenance for a functioning product or service. Depending on the field, it can have slightly different meanings.

In engineering, maintainability is the ease with which a product can be maintained to:

• correct defects or their cause,
• Repair or replace faulty or worn-out components without having to replace still working parts,
• prevent unexpected working conditions,
• maximize a product's useful life,
• maximize efficiency, reliability, and safety,
• meet new requirements,
• make future maintenance easier, or
• cope with a changing environment.

In some cases, maintainability involves a system of continuous improvement - learning from the past to improve the ability to maintain systems, or improve the reliability of systems based on maintenance experience.

In telecommunications and several other engineering fields, the term maintainability has the following meanings:

• A characteristic of design and installation, expressed as the probability that an item will be retained in or restored to a specified condition within a given period of time, when the maintenance is performed by prescribed procedures and resources.
• The ease with which maintenance of a functional unit can be performed by prescribed requirements.

 This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22. (in support of MIL-STD-188).

In software engineering, these activities are known as software maintenance (cf. ISO/IEC 25010).^[1] Closely related concepts in the software engineering domain are evolvability, modifiability, technical debt, and code smells.

• List of system quality attributes, non-functional requirements for system evaluation
• Maintenance (technical), measures to preserve or restore the functionality or lifespan of equipment and infrastructure
• Supportability (disambiguation)
• Serviceability (disambiguation)
• Software sizing, activity in software development to estimate the size of a component, such as the number of lines of code or functions (not taking into account the effort required)
• Reliability, availability, maintainability and safety, characterization of a product or system
• Throw-away society, human society strongly influenced by consumerism

• Blanchard, Benjamin S.; Verma, Dinesh C.; Peterson, Elmer L. (1995). Maintainability: A Key to Effective Serviceability and Maintenance Management. Wiley. ISBN 978-0-471-59132-0.
• Ebeling, Charles E. (2019). An Introduction to Reliability and Maintainability Engineering (3rd ed.). Waveland Press. ISBN 978-1-4786-3933-6.
• Patton, Joseph D. (2005). Maintainability & Maintenance Management (4th ed.). Patton Consultants. ISBN 978-1-55617-944-0.

• "Calculation, Field testing and history of Maintainability Index (MI) (with references)". Virtual Machinery. Archived from the original on 2012-01-20.
• "Measurement of Maintainability Index (MI)". Verifysoft Technology GmbH. Archived from the original on 2011-06-23.* Foreman, John T.; Gross, Jon; Rosenstein, Robert; Fisher, David; Brune, Kimberly (January 1997). "Maintainability Index Technique for Measuring Program Maintainability". C4 Software Technology Reference Guide: A Prototype (PDF). Software Engineering Institute. p. 231. CMU/SEI-97-HB-001. Archived (PDF) from the original on 2022-10-09.