Depreciation is a systematic & rational process of distributing the cost of tangible assets over the life of assets.
Depreciation is a process of allocation of the cost of asset.
Cost to be allocated = acquisition cot - salvage value.
Allocated over the estimated useful(Economic) life of assets.
Allocation method should be systematic & rational.
Depreciation methods which are based on time
Straight line method
Declining balance method
Depreciation based on use (activity) of the asset