When a company acquires assets, those assets usually come at a cost. However, because most assets don't last forever, their cost needs to be proportionately expensed based on the time period during which they are used. Amortization and depreciation are methods of prorating the cost of business assets over the course of their useful life.

Amortization
Amortization is a method of spreading the cost of an intangible asset over a specific period of time, which is usually the course of its useful life. Intangible assets are non-physical assets that are nonetheless essential to a company, such as patents, trademarks, and copyrights. The goal in amortizing an asset is to match the expense of acquiring it with the revenue it generates.

Let's say a company spends $50,000 to obtain a license, and the license in question will expire in 10 years. Since the license is an intangible asset, it should be amortized for the 10-year period leading up to its expiration date. Using the straight-line method of amortization, which is a method for charging a cost to an expense at a consistent rate over time, the company's annual amortization expense for the license will be $5,000 (that's $50,000/10 years), meaning the asset will decline in value by $5,000 every year.

Depreciation
Like amortization, depreciation is a method of spreading the cost of an asset over a specified period of time, typically the asset's useful life. The purpose of depreciation is to match the expense of obtaining an asset to the income it helps a company earn. Depreciation is used for tangible assets, which are physical assets such as manufacturing equipment, business vehicles, and computers. Depreciation is a measure of how much of an asset's value has been used up at a given point in time.

Let's say a company purchases a new piece of equipment with an estimated useful life of 10 years for the price of $100,000. Using the straight-line method, the company's annual depreciation expense for the equipment will be $10,000 ($100,000/10 years). This is important because depreciation expenses are recognized as deductions for tax purposes. It is also possible for a company to use an accelerated depreciation method, where the amount of depreciation it takes each year is higher during the earlier years of an asset's life.

Differences
The key difference between amortization and depreciation is that amortization is used for intangible assets, while depreciation is used for tangible assets. Another major difference is that amortization is almost always implemented using the straight-line method, whereas depreciation can be implemented using either the straight-line or accelerated method. Finally, because they are intangible, amortized assets do not have a salvage value, which is the estimated resale value of an asset at the end of its useful life. Depreciated assets, by contrast, often have a salvage value. An asset's salvage value must be subtracted from its cost to determine the amount in which it can be depreciated. 

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