Final answer:
Straight-line depreciation is a method of reducing the value of an asset uniformly over its useful life and is considered a fixed cost because it remains consistent irrespective of production levels.
Step-by-step explanation:
Straight-line depreciation is a method where the value of a tangible asset is reduced uniformly over its useful life. When discussing expenditures that do not change regardless of the level of production, one key term comes to mind: fixed cost. Straight-line depreciation is actually an example of a fixed cost, not a variable cost, step-variable cost, mixed cost, or curvilinear cost, because it does not fluctuate with the level of production or sales volume.
Rent on a factory or machinery acquisition costs are common examples of fixed costs, similar to how depreciation works on capital assets. In the context of cost accounting and financial reporting, straight-line depreciation ensures that the cost of an asset is evenly spread out over the time it is expected to be used.