What term is used to describe when a system is not available?

The term that describes when a system is not available is "downtime." Downtime refers specifically to periods when a computer system or network is not operational or accessible, which can result from various reasons such as technical malfunctions, maintenance, power failures, or unforeseen issues. It is an important metric for assessing system reliability and performance, as downtime directly affects end-users and operational efficiency.

In contrast, the other terms relate to different aspects of system performance. Latency refers to the delay before a transfer of data begins following an instruction for its transfer, rather than the complete unavailability of a system. Outage typically denotes a temporary failure of functionality, which could align closely with downtime but is often used more specifically when an unexpected failure occurs. Maintenance refers to the scheduled processes set to keep a system in working order, which may involve temporary downtime but is a proactive measure rather than a result of failure or availability issues.