The dividing line between the bright and shaded regions of the disk of the moon or an inner planet.

明暗界线：月亮或内行星亮和暗的区域之间的分界线。

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The dividing line between the bright and shaded regions of the disk of the moon or an inner planet.

明暗界线：月亮或内行星亮和暗的区域之间的分界线。

youdao