How to say "estuary" in Japanese

• 河口かこうCommon
  no-adjectiveThe everyday word for the mouth of a river where it meets the sea, covering the ordinary sense of 'estuary'. Use it in general description and conversation, e.g. when talking about a port or scenery.
• 感潮域かんちょういき
  nounA technical term for the tidal reach or estuarine basin — the stretch where tides influence the water. Suited to geography, hydrology and ecology writing rather than everyday description.
• 三角江さんかくこう
  nounA less common technical term for an estuary viewed as a landform, literally a triangular inlet at a river's mouth. Rare outside geography texts, it is seldom the word you want in ordinary usage.

Use 河口 for a river mouth in everyday contexts; use 感潮域 for the tide-influenced zone as a geographic or ecological term, and 三角江 for estuaries emphasized as triangular coastal shapes.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 河口かこうmouth of river
• 感潮域かんちょういきestuary
• 三角江さんかくこうestuary