Maintainability refers to the relative ease and cost of maintaining an entity over its lifetime, including fixing, updating, extending, operating, and servicing it. An entity with low costs in these areas is considered maintainable, while an entity with high costs may be considered unmaintainable or high maintenance. The following are illustrative examples.

Repairs
A high speed train offers diagnostic features that reduce the turnaround time of repairs.

Reliability
An IT service has 99.999% availability with no serious incidents in its operating history.

Durability
Wet infrastructure that operates reliably for over a century without a major overhaul.

Efficiency
A heating ventilation and air conditioning system that remains energy efficient after a decade of use.

Updates
A software platform offers an administrative tool that allows organizations to review the release notes of available updates and apply them as required.

Preventative Maintenance
A component of an aircraft automatically warns operational teams that an operating parameter such as temperature is abnormal. This allows maintenance to occur before damage worsens.

Scheduled Maintenance
An electric car manufacturer publishes an accurate 7-year maintenance schedule such that owners know upfront what is required to keep the vehicle operating safely.

Extensions
A software product that is easy to extend with new functionality. For example, code with a clear structure and good smell.