耐力 (nàilì) literally combines 耐 (nài), meaning 'to endure' or 'to withstand', and 力 (lì), meaning 'strength' or 'power'. Together, they form a noun meaning 'stamina' or 'endurance' — the physical or mental capacity to sustain prolonged effort, stress, or hardship without tiring. It is commonly used in contexts related to sports, fitness, health, and personal resilience.

This word emphasizes sustained performance over time rather than short bursts of power. You’ll hear it in discussions about training for marathons, recovering from illness, or maintaining focus during long study sessions. Unlike strength (力量) or speed (速度), 耐力 highlights persistence and resistance to fatigue. It’s neutral in register — appropriate in both formal reports and everyday conversation — and often appears with verbs like 提高 (tígāo, 'to improve'), 增强 (zēngqiáng, 'to strengthen'), or 缺乏 (quēfá, 'to lack').