海洋|かいようkaiyou[0]heiban (flat)

1. nounocean; sea
   ロブスターは海洋かいよう動物どうぶつの一種いっしゅに属ぞくします。↗

   Lobsters belong to a class of marine animals.

• Synonym海原うなばらWrittenPoetic, literary word for the vast, open sea, seen mainly in poetry and song lyrics; unlike 「海洋」 it carries lyrical colour, not an academic or formal tone.
• Synonym大洋たいようNeutralRefers to the great oceans — Pacific, Atlantic and so on, as in 「五大洋」; 「海洋」 is a general term for seas, including coastal waters.
• SynonymオーシャンNeutralLoanword often seen in product and shop names, e.g. 「オーシャンビュー」; 「海洋」 is the academic, formal choice.
• Synonym海うみNeutralThe everyday, most common word for the sea; 「海洋」 belongs to academic and policy contexts, as in 「海洋汚染」.
• Synonym大海たいかいWrittenA literary word for the vast sea, known from the proverb 「井の中の蛙大海を知らず」; 「海洋」 is the academic term.
• Related外洋がいようWrittenWritten word for the open sea far from land, as in 「外洋航海」; 「海洋」 is a general term covering all seas.
• Related遠海えんかいWrittenWritten term for waters distant from the coast, the opposite of 「近海」; 「海洋」 is a general term for the sea.
• Related外海がいかいNeutralThe sea outside a bay or far from land, the opposite of 「内海」; 「海洋」 is the general, collective term.
• Related大海原おおうなばらWrittenPoetic, literary word for the boundless sea, common in lyrics and literature; 「海洋」 is an academic term without that flavour.
• Antonym陸地りくちNeutralAntonym on the land–sea divide: land as opposed to the sea, as in 「陸地と海洋の面積」.
• Antonym陸りくCasualNot actually an antonym here: this 「陸（ろく）」 is a variant of 「碌」 meaning decent or satisfactory; land as opposed to sea is read 「りく」, or say 「陸地」.

Use 「海洋」 in academic and policy contexts, e.g. 「海洋汚染」; in everyday speech say 「海」. For the five great oceans use 「大洋」; for poetic, literary flavour use 「海原」 or 「大海原」. The antonym is 「陸地」.

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

1. 海うみと同意どうい。漢語かんご的てきであり、形式的けいしきてき・正式せいしきな語句ごくに用もちいられる。例れい）海洋学かいようがく、海洋かいよう研究所けんきゅうしょ