An expense that is supposed to reflect the loss in value of a fixed asset. For example, if a machine will completely wear out after ten year’s use, the cost of the machine is charged as an expense over the ten‐year life rather than all at once, when the machine is purchased. Straight line depreciation charges the same amount to expense each year. Accelerated depreciation charges more to expense in early years, less in later years. Depreciation is an accounting expense. In real life, the fixed asset may grow in value or it may become worthless long before the depreciation period ends.