EBITDA is defined as net income plus or minus net interest plus income taxes, depreciation and amortization. Adjusted EBITDA further excludes (i) non-cash items (e.g., stock-based compensation expense and non-cash pension and postretirement expense) and (ii) items that management does not consider to be useful in assessing our operating performance (e.g., acquisition-related costs, restructuring charges, income or loss from discontinued operations, and gain or loss on sale of assets). Adjusted earnings per diluted share exclude similar items as adjusted EBITDA. None of these non-GAAP financial measures are recognized terms under GAAP and do not purport to be an alternative to net income as an indicator of operating performance or any other GAAP measure.
Management uses these non-GAAP measures in its operational and financial decision-making, believing that it is useful to eliminate certain items in order to focus on what it deems to be a more reliable indicator of ongoing operating performance and our ability to generate cash flow from operations. As a result, internal management reports used during monthly operating reviews feature the adjusted EBITDA and adjusted earnings per diluted share metrics. Management also believes that investors may find non-GAAP financial measures useful for the same reasons, although investors are cautioned that non-GAAP financial measures are not a substitute for GAAP disclosures. EBITDA, adjusted EBITDA, and adjusted earnings per diluted share are also used by many of our investors, research analysts, investment bankers, and lenders to assess our operating performance. For example, a measure similar to adjusted EBITDA is required by the lenders under our term loan and revolving credit agreement.
Because not all companies use identical calculations, our presentation of non-GAAP financial measures may not be comparable to other similarly-titled measures of other companies. However, these measures can still be useful in evaluating our performance against our peer companies because management believes the measures provide users with valuable insight into key components of GAAP financial disclosures. For example, a company with greater GAAP net income may not be as appealing to investors if its net income is more heavily comprised of gains on asset sales. Likewise, eliminating the effects of interest income and expense moderates the impact of a company's capital structure on its performance.