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to go out of use; to become obsolete; to die out; to go out of fashion; to go out of style
to decline (e.g. of morals); to be lost; to go into decline (of a town, business, etc.)
伝統工芸は廃れる一方だ。
Traditional crafts are increasingly falling out of use.
あのファッションはもう完全に廃れた。
That fashion style has completely gone out of fashion.
若者が使わなくなり、この方言は廃れていくだろう。
As young people stop using it, this dialect will probably die out.