靠小鋼珠轉動的零件，以及裡面的那顆球
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rolling machine part · noun · B2
A machine part made of small hard balls held in a ring, fitted around a shaft or inside a wheel so that it turns smoothly with very little rubbing.
滾珠軸承
Think of two metal rings, one inside the other, with a circle of small steel balls trapped between them. When the inner ring turns, the balls roll instead of dragging, so the whole thing spins for a long time on one push. Ball names the little balls; bearing names the part that carries the weight and lets it turn.
可以想成兩個金屬圈，一個套在另一個裡面，中間夾著一圈小鋼珠。裡面的圈一轉，球就跟著滾，不是用磨的，所以推一下可以轉很久。ball 指的是那些小球，bearing 指的是承著重量、讓東西轉起來的零件——這個詞的兩個用法，差別只在你數的是整組還是其中一顆。
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