Decrease in value of an asset due to obsolescence or use WordNet 3.0 & Open English WordNet

In accountancy, depreciation is a term that refers to two aspects of the same concept: first, an actual reduction in the fair value of an asset, such as the decrease in value of factory equipment each year as it is used and wears, and second, the allocation in accounting statements of the original cost of the assets to periods in which the assets are used. Wikipedia

The decline in value of assets. Wiktionary

Damage or depreciation resulting from ordinary use (normally as something excluded from a guarantee or warranty of quality, or as justifying a write-down in a set of accounts). Wiktionary

Damage or depreciation. Wiktionary (translation)