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entrance door; front door
gateway (to a region, etc.)
配達員が玄関口に立っていた。
The delivery person was standing at the front door.
成田空港は、世界の国々との国際交流の玄関口です。
Narita Airport is Japan's gateway for international exchange with countries around the world.
この港は地域の経済の玄関口となる。
This port will become the economic gateway for the region.