drain是引流管，drainage是引流的意思吧。查到的：

来源: 妖妖灵 于 2022-08-17 07:26:51 [] [博客] [旧帖] [给我悄悄话] 阅读数 : (950 bytes)

Drain: A channel or pipe carrying off surplus liquid, esp.rainwater or liquid waste. Drainage: The means of removing surplus water or liquid waste; a system of drains.

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