凹

A pictograph showing a surface indented inward at the center.

Direct antonym to 凸, designed as a complementary character pair.

Semantic range:

- concave, hollow, sunken;

- by extension: indentation, depression, cave-in;

- antonym of 凸 (convex, protruding).

凹凸 (요철) — unevenness, irregular surface, convex–concave pattern

Less prominent than 凸 in modern slang, but visually striking due to its symmetry and similarity to the Hangul letter ㅂ.

Occasionally seen in playful substitutions (e.g. 凹人 used humorously in place of “people” characters, for its shape).

In Japanese slang, paired with 凸 as デコボコ (deko-boko) meaning “uneven, bumpy, mismatched.”