Tiredness is the heavy, dragging feeling you get when your body and mind need rest. After a long day of school, sports practice, and homework, tiredness settles into your muscles and makes your eyes want to close. Your thoughts slow down, your body feels sluggish, and climbing stairs seems like climbing a mountain.

Tiredness happens because your body uses energy constantly: your brain works through math problems, your muscles carry you around, your heart pumps blood. Eventually, you run low on energy, like a phone battery dropping toward zero. Sleep recharges you, giving your body time to repair itself and your brain time to organize everything you learned that day.

Not all tiredness is the same. Physical tiredness comes from running around or working hard with your body. Mental tiredness comes from concentrating intensely, like after taking a difficult test. Sometimes people feel tired because they're bored or unmotivated, which is different from genuine physical exhaustion.

The word fatigue means roughly the same thing but sounds more medical or serious. Extreme tiredness that doesn't improve with rest might signal illness and needs a doctor's attention. But ordinary tiredness is simply your body's way of saying: time to rest and recharge.