Weighted Average Cost of Capital — the blended after-tax cost of a firm's permanent capital, used as the discount rate for unlevered free cash flows in a DCF: WACC = r_d(1-t) · (D)/(D+E) + r_e · (E)/(D+E). Weights are TARGET capital-structure weights at market value; the debt term is tax-effected to reflect the interest tax shield; the cost of equity r_e is typically derived from CAPM with a relevered beta.