Obsolescence is the state of being which occurs when an object, service, or practice is no longer maintained or degraded even though it may still be in good working order.The international standard EN62402 Obsolescence Management - Application Guide defines obsolescence as being the "transition from availability of products by the original manufacturer or supplier to unavailability".
Obsolescence frequently occurs because a replacement has become available that has, in sum, more advantages compared to the disadvantages incurred by maintaining or repairing the original.
Obsolete also refers to something that is already disused or discarded, or antiquated. Typically, obsolescence is preceded by a gradual decline in popularity.