The probability that a product functions as required for a given duration under given conditions without a function-ending event.
Reliability is the probability that a product will continue to function as required for a given duration under given conditions without suffering a function-ending failure. It is therefore a measurable performance concept rather than a vague quality claim.
Do not use reliability as a loose synonym for quality or durability. The useful record includes the function, conditions, duration, probability basis, and failure definition.
In ESPR, reliability is not the same as durability. Reliability is a probability concept tied to function, duration, and conditions; durability is broader product ability to maintain function and performance over time.
Track reliability together with test basis, operating conditions, duration, function affected, and maintenance assumptions. That makes it easier to compare products and support claims without overgeneralizing.
Regulation (EU) 2024/1781 establishing a framework for the setting of ecodesign requirements for sustainable products
the probability that a product functions as required under given conditions for a given duration without an occurrence which results in a primary or secondary function of the product no longer being performed;
Reference: Article 2, point 23
Implementation records should capture the reliability claim, duration condition, test method, failure event, operating conditions, probability basis, product model, and distinction from durability, service life, or absence of recorded defects.
Reliability is a probability-performance control: the evidence consequence is that longevity claims can be tied to duration, conditions, methods, and failure criteria instead of being treated as broad quality language.