Stamina is the strength you need to keep going for a long time. It is not about doing one big, strong thing — that is different. A person who can lift a very heavy box has strength. A person who can walk for six hours has stamina. So stamina is about time: how long you can keep doing something before your body or your mind stops you. We use it for the body most of the time. Runners, swimmers, football players, soldiers, farmers, nurses on a night shift — all of these need stamina. "She has good stamina." "He has no stamina." "My stamina is getting better." But we also use it for the mind, and this is very common. Sitting and studying for four hours is hard, and English speakers will call that stamina too. "Reading a long book takes stamina." "I don't have the mental stamina for another meeting today." Teachers say it about students; office workers say it about long projects. So if a job is long and boring and tiring, and someone keeps going anyway, that is stamina. It is an uncountable noun. We say "a lot of stamina", "more stamina", "good stamina" — never "a stamina" and never "staminas". It is a normal word, not formal and not slang, and you can use it in class, in an email, or with friends. In sports writing and in video games you will meet it constantly — many games have a green stamina bar that goes down when your character runs. One more thing. People often use it loosely to mean "energy today", but the true meaning is closer to a trained ability, something you build over months. That is why "build stamina" and "lose stamina" are such common phrases: it goes up and down slowly, like a savings account, not like a mood.

耐力、體力（持久的那種）。運動場上講「耐力」最自然；講唸書、開會撐得住，可以說「持久力」或「續航力」。注意不要只翻成「體力」——「體力」偏一時的力氣，stamina 是能撐多久。