depreciation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A decrease or loss in value, as because of age, wear, or market conditions.
• noun Accounting An allowance made for a loss in value of property.
• noun Reduction in the purchasing value of money.
• noun An instance of disparaging or belittlement.

from The Century Dictionary.

• noun The act of lessening or bringing down price or value.
• noun A fall in value; reduction of worth.
• noun A belittling or running down of value or merit; conscious undervaluation or underestimation of the merits of a person, action, or thing; unfavorable judgment or scant praise: as, he is much given to the depreciation of even his best friends.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of lessening, or seeking to lessen, price, value, or reputation.
• noun The falling of value; reduction of worth.
• noun the state of being depreciated.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The state of being depreciated.
• noun The decline in value of assets.
• noun accounting The measurement of the decline in value of assets. Not to be confused with impairment, which is the measurement of the unplanned, extraordinary decline in value of assets.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun decrease in value of an asset due to obsolescence or use
• noun a decrease in price or value
• noun a communication that belittles somebody or something