河口

1. Origins, structure, and basic meaning

• Structure: 河口 combines 河, “river,” with 口, “opening,” and is a geographic noun read かこう.
• Basic usage: It denotes the mouth where a river enters a larger body of water and the area around it.
  • 河口の近くでは川幅が急に広くなります。 describes the river widening near its mouth, while 渡り鳥を観察するために河口へ出かけました。 makes the estuary the outing destination.

2. Common pitfalls and similar expressions

• 河口の近く
  • の links 河口 with 近く to mean “near the river mouth,” distinguishing the mouth itself from its surrounding area.
• 河口へ出かける
  • へ marks the direction or destination of the outing, and ために gives observing migratory birds as its purpose.
• River mouth and estuary
  • “River mouth” is the broad basic equivalent of 河口. “Estuary” fits when emphasizing a widened, tidal environment, but do not impose that narrower technical sense without context.