A condition inferior to an earlier condition; a gradual falling off from a better state WordNet 3.0

A condition inferior to an earlier condition; a gradual falling off from a better state; decline Open English WordNet

Decline involves change over time, for example: from previously efficient to inefficient organizational functioning from previously rational to non-rational organizational and individual decision-making from previously law-abiding to law-violating organizational and individual behavior from previously virtuous to iniquitous individual moral behaviorNote: distinguish the noun decline from the adjective obsolete. Wikipedia

The act or state of falling off or declining from excellence or perfection; deterioration; decay; decline. Wiktionary