When the assets of the company are written off over a number of years for the purpose of their replacement or renewal and not depending on the life of asset is termed as amortization. It is different from depreciation, which is periodic writing off of the asset based on its normal life expectancy.

Impairment can be termed as the fall in the value of the asset due to any physical damage to the asset, obsolescence, or due to technological innovation. Impairments can be written off. Simply you can say that impairment is the difference between the fair value and the carrying value of an asset.