this radio can fit in the palm of my hand.

This radio can fit in the palm of my hand.

这收音机体积小到我可一手掌握。

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如果某东西能fit in the palm of one's hand 表明这东西迷你到能一手掌握。如果某人或某事是in the palm of one's hand也可表示在某人的掌控之中。

例：
Everything is in the palm of my hand.一切尽在我的掌握之中。
He is in the palm of my hand.他逃不出我的五指山。