海王星
Kaiōsei[ka̠io̞ːse̞ː]
In Japanese, Neptune is referred to as 海王星 (Kaiōsei). Wiktionary also lists ネプチューン (Nepuchūn) and ネプトゥーン (Neputūn).
Meaning: eighth planet of the solar system (name)
Ways to say it
| Japanese | Romanization (Wiktionary) | IPA | Note |
|---|---|---|---|
| 海王星 | Kaiōsei | [ka̠io̞ːse̞ː] (narrow) | |
| ネプチューン | Nepuchūn | [ne̞pɯ̟t͡ɕɨ̃ːɴ] (narrow) | katakana |
| ネプトゥーン | Neputūn | katakana |
The term 海王星 is used to name the eighth planet of the solar system.
What does it mean word for word?
The term 海王星 can be understood to mean "sea king star".
Which one should you use?
海王星 is the standard scientific term used in astronomy and textbooks. In contrast, the katakana forms ネプチューン and ネプトゥーン are transliterations of the English name 'Neptune'.
How do you pronounce it?
Kaiōsei
Did you know?
- The characters for 海王星 were originally borrowed from Chinese, reflecting how much Japanese scientific terminology relies on Sino-Japanese vocabulary.
- While the katakana forms like ネプチューン are used for the planet, they are also used when discussing the Roman god 'Neptune' in a mythological context.
- If you see the word 海王 (Sea King) without the 星 (Star), it can sometimes be used as a nickname for characters in Japanese pop culture with water powers.
Examples in context
- 海王星は太陽系の8番目の惑星だ。Neptune is the eighth planet of the solar system.This sentence is useful for stating that Neptune is the eighth planet of the solar system.Tatoeba #185081 by tommy_san, translation #22212 by CK
- 海王星は暗く寒く、かつ烈風が吹き荒れている。Neptune is dark, cold, and very windy.This sentence is useful for describing the dark, cold and windy nature of Neptune.Tatoeba #6855693 by Sonata, translation #5322679 by Hybrid
- 海王星は太陽系の8番目の惑星です。Neptune is the eighth planet in the solar system.
- 海王星は青い色をしている。Kaiousei wa aoi iro o shite iru.Neptune is blue in color.
Example conversation
Two students are looking at a star chart in a library.
- 大翔 Hiroto海王星はどこにあるかな？Kaiousei wa doko ni aru kana?I wonder where Neptune is?
- 結衣 Yuiあそこだよ、大翔君。Asoko dayo, Hiroto-kun.It is over there, Hiroto.
- 大翔 Hiroto本当だ、見つけたよ。Hontou da, mitsuketa yo.You're right, I found it.
- 結衣 Yuiすごく遠いところにあるね。Sugoku tooi tokoro ni aru ne.It is in a very distant place, isn't it?
Sources
- Wiktionary, “neptune” translations and entries 海王星, ネプチューン, CC BY-SA 4.0, dump of 2026-09-26.
- Word origins: Wiktionary entries 海王星, CC BY-SA 4.0.
- Example sentences: Tatoeba CC BY 2.0 FR.
