Refers to the physical or mental ability to sustain prolonged effort; often used in sports, fitness, and perseverance contexts.
Marathons require stamina.
He has endurance, so he can stay focused even during long study sessions.
持久力 is the formal, technical term for endurance used in sports science, whereas スタミナ is the casual loanword people use in everyday speech.
Compound of 持久 (jikyū, 'endurance') + 力 (ryoku, 'power'). The exact historical derivation is uncertain, but the kanji composition transparently conveys the meaning of sustained strength.