has worn是什么时态
has worn是现在完成时，现在完成时( The Present Perfect Tense)是过去的动作或状态持续到现在，对现在造成的影响，可能持续发生下去。
Notice how the tread on this tyre has worn down.
注意这个轮胎的花纹磨损的程度。
This bottom of the bucket has worn through.
这个桶底已经磨穿了。
The material has worn thin.
这种布料已穿薄了。
The inscription has worn away.
Your car has worn brake shoes.
你的车装上了制动蹄片。