洪 — “Deluge / Flood / Vast” in Japanese

Master (高手)こう

Radical ⽔ · radical 85 The building block this kanji is filed under

“Deluge / Flood / Vast” in Japanese is 洪, read kou (こう). It is a Jōyō kanji taught in Japanese secondary school (junior & senior high) — the 高手 · Master tier beyond the grade 1–6 Kyōiku set, and appears in words such as 洪水 (flood).

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What does 洪 mean?

Full details, readings & example

Kanji	洪
Meaning	Deluge / Flood / Vast
Readings	こう
Grade	Master (高手 · secondary school)
Curriculum	Jōyō kanji · Japanese secondary school (JLPT N1–N2)
Example	洪水 (flood)

How to read 洪

洪 is read kou (こう) depending on the word.

Words with 洪

洪水こうずい

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Kanji read the same way as 洪

Same sound, different character — the classic trap. Compare them side by side:

Updated: 2026-08-28