Definicja straight-line depreciation from APC

A uniform distribution of the acquisition and production costs of a fixed asset over its entire useful life.

The periodic depreciation amounts are equal to the acquisition and production costs divided by the entire useful life.

If there are subsequent acquisitions to the asset, the depreciation amounts increase by the amount of the subsequent acquisition divided by the original useful life.

The actual depreciation period (the period up to the point when the book value reaches zero) must be increased if there are subsequent acquisitions.