水平線|すいへいせんsuiheisen

1. nounhorizon (related to bodies of water)
   太陽たいようが水平線すいへいせんの下したに沈しずんだ。↗

   The sun sank below the horizon.

• Synonym視水平線WrittenA surveying term for the horizontal line visible to the observer; specialist, written usage.
• Related地平線ちへいせんNeutralNeutral word for the line where the land meets the sky, the counterpart of 「水平線」 at sea.
• RelatedスカイラインNeutralA loanword for the skyline of city buildings or a scenic mountain road; neutral in register.
• Related地平ちへいWrittenA written word covering flat, level ground as well as the horizon; mostly used in compounds.
• Related視地平しちへいWrittenA written term with an academic astronomical flavour, meaning the apparent horizon; keep it to formal prose.
• Related視地平線WrittenA written, academic term for the horizon as it appears to the eye, used in astronomical surveying; 「水平線」 is the line where sea meets sky.

Use 「水平線」 for the line where the sea meets the sky. For land use 「地平線」, for a city skyline 「スカイライン」, and for astronomical surveying the technical 「視地平線」. 「視水平線」 and 「視地平」 are specialist written terms; 「地平」 appears mostly in compounds.

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

1. 海うみと空そらとの境界きょうかいがなす線せん。
2. 重力じゅうりょくと垂直すいちょくな方向ほうこうに伸のびる線せん。水平すいへいな線せん。