Something that is worn out is so old, damaged, or thin from use that it cannot be used anymore.
Car buyers tend to replace worn-out tyres with the same brand.
汽车的买主们在更换废旧轮胎时依然倾向于选择同一品牌。
Someone who is worn out is extremely tired after hard work or a difficult or unpleasant experience.
Before the race, he is fine. But afterwards he is worn out.
比赛前,他状态良好。但在赛后,他就疲惫不堪了。