Form Clearance (cF) is the radial depth of involute profile beyond the depth of engagement with the mating part.

齿形裕度：齿形裕度(cF)是相互配合的内、外花键的渐开线齿廓超过结合部分的径向距离。

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To make the part interchangeable, each individual part must be made to a size that will fit the mating part in the correct way.

为了使零件能够互换，每个零件作出的大小必须能准确地适用于与其匹配的零件。

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The male hen harrier is famous for its spectacular looping "sky-dance", part of an elaborate mating ritual.

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Sub-Saharan Africa and the Caribbean (the second-worst affected part of the world) have particularly high levels of disassortative mating between young girls and older men.

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