obsolescence

obsolescence　陈旧　

Significant decline in the competitiveness，usefulness，or value of an article or property.Obsolescence is important to operate risk，and occurs generally due to the availability of alternatives that perform better or are cheaper or both，or due to changes in user preferences，requirements，or.It is distinct from fall in value（depreciation）due to physical deterioration or normal wear and tear.It requires to write off of the value of the obsolete item against earnings to comply with the accounting principle of showing inventory at lower of cost or market value.