Ageing 1
Ageing 1 : General process in which characteristics of a structure, system or component gradually change with time or use. Although the term ageing is defined in a neutral sense - the changes involved in ageing may have no effect on protection or safety, or could even have a beneficial effect - it is most commonly used with a connotation of changes that are (or could be) detrimental to protection and safety (i.e. as a synonym of ageing degradation)