What does 海王星 mean?
海王星 is a Japanese noun meaning “neptune” in English. It is written as 海王星 in kanji, かいおうせい in hiragana, and kaiousei in romaji. This word is part of JLPT N3 vocabulary.
Example sentence
海王星は太陽系の8番目の惑星だ。
Neptune is the eighth planet of the solar system.