Depreciation is the reduction of the value of a property or chattel as a result of the passing of time (i.e. a new car may be worth $20,000.00, $18,000.00 after one year, $16,000.00 after two years etc.). Usually used for tax purposes, the depreciation in the value of a property may be used as a tax deduction. If a property or chattel loses its value quickly, this depreciation rate may be accelerated so that most of the value is lost in the first few years and then the depreciation rate decreases later in the propertys life span. Also known as Writing down the value of a property (or a chattel).