可恃性(廣義的可靠度)為時間品質或時間性能 (quality over time or performance over time),而且是在交貨以後的時間。根據 IEC 的定義,可恃性是可用度的通用名詞,是指交貨以後任何一時刻,物品可以維持在良好(功能正常)狀態的能力的綜合性指標,其影響因子包括可靠度、維護度與維護支援(支援度)等。
IEC 60050-191_2014, International Electrotechnical Vocabulary Chapter 191: Dependability and quality of service
IEC 60300-1_2014 (ed 3.0), Dependability management - Part 1: Guidance for management and applications
IEC 60300-1_2003 (ed 2.0), Dependability management - Part 1: Dependability management systems
IEC 60300-1_1994 (ed 1.0) = ISO 9000-4_1994, Dependability management - Part 1: Dependability programme management
IEC 60050-191_1990, International Electrotechnical Vocabulary Chapter 191: Dependability and quality of service
IEC 60300_1984, Reliability and maintainability management
IEC 60300_1969, Managerial aspects of reliability
國際品質標準 ISO 9000 系列中,品質詞彙 ISO 9000,在 2005 年改版時,保留可恃性的定義,「可恃性是描述可用度性能的集合名詞,其影響因子包括可靠度性能、維護度性能與維護支援性能。」並沒有有關可靠度的直接定義:
ISO 9000:2005, 3.5.3 Dependability
Collective term used to describe the availability performance and its influencing factors: reliability performance, maintainability performance and maintenance support performance.
NOTE. Dependability is used only for general descriptions in non-quantitative terms. [IEC 60050-191:1990]