obsolescence /ˌɑːbsəˈlɛsn̩s/ noun Learner's definition of OBSOLESCENCE
[noncount]
: the condition of no longer being used or useful : the condition of being obsolete废弃；淘汰；过时 -
the obsolescence of the old technology旧技术的淘汰
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Once a useful tool, slide rules have fallen into obsolescence.计算尺曾经是有用的工具，现在已经被淘汰了。
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built-in/planned obsolescence [=the practice of making or designing something (such as a car) in such a way that it will only be usable for a short time so that people will have to buy another one]内在/计划陈旧产品（故意制造或设计成不耐使用的产品，以迫使人们购买新的）