他们听上去都是拟声词 flip音节短促尖锐 用以描述快捷疾速的动作.flip-flop的发音模拟快速往复的动作.flap听上去不正象旗帜和船帆在风中拍打的声音吗?
"Flip" is a short, sharp word for a short, sharp action. "Flip-flop" arose in imitation of the action of going quickly back and forth.
要生产泵动作用，它包括往复运动的活塞或旋转叶片。
To produce the pumping action, it contains pistons that are driven back and forth, or rotating vanes.
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