How does the range-payload tradeoff work in aircraft design?

Range and payload are inversely related given fixed MTOW. The range-payload diagram shows: Maximum payload, minimum range - Aircraft at MTOW, maximum payload limited by ZFW, minimum fuel; Design point - Typical mission with specified payload and range; Maximum range, reduced payload - Payload reduced to add fuel up to MTOW; Ferry range - Zero payload, maximum fuel, maximum range possible. Physics: Adding fuel weight reduces payload capacity, more weight requires more fuel to fly same distance (diminishing returns). The Breguet range equation (R = V/SFC * L/D * ln(Wi/Wf)) shows range depends on efficiency (L/D, SFC), speed, and fuel fraction. Airlines operate within the diagram based on route demands. Design point placement affects aircraft competitiveness for different markets.