凹 — “Concave / Hollow / Sunken” in Japanese

Master (高手)おう, くぼ, へこ, ぼこ

Radical ⼐ · radical 17 The building block this kanji is filed under

“Concave / Hollow / Sunken” in Japanese is 凹, read ou, kubo, heko (おう, くぼ, へこ, ぼこ). 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 凹凸 (unevenness).

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What does 凹 mean?

Full details, readings & example

Kanji	凹
Meaning	Concave / Hollow / Sunken
Readings	おう, くぼ, へこ, ぼこ
Grade	Master (高手 · secondary school)
Curriculum	Jōyō kanji · Japanese secondary school (JLPT N1–N2)
Example	凹凸 (unevenness)

How to read 凹

凹 is read ou (おう) or kubo (くぼ) or heko (へこ) or boko (ぼこ) depending on the word.

Words with 凹

凸凹
凹凸

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Kanji read the same way as 凹

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

Updated: 2026-08-28