What are the key weight definitions used in aircraft design?

Key aircraft weights: Empty Weight (OEW/MEW) - Structure, engines, systems, unusable fuel, basic equipment; Operating Empty Weight (OEW) - Empty weight plus crew and operational items; Payload - Passengers, cargo, mail (revenue-generating load); Fuel - Mission fuel plus reserves; Zero Fuel Weight (ZFW) - OEW plus payload (structural limit protecting wing bending); Maximum Takeoff Weight (MTOW) - Maximum certified weight for takeoff; Maximum Landing Weight (MLW) - Maximum certified landing weight (lower due to gear/structural limits); Maximum Ramp Weight (MRW) - MTOW plus taxi fuel. Weight management is critical: empty weight directly reduces payload or range capability. Design targets empty weight fraction (empty/MTOW) typically 0.5-0.6 for transports.