KanjiJLPT N1
Concave

concave, hollow, sunken

Mnemonic

Surface that dips down in the middle — a concave shape.

Details

The keyword for 凹 is concave. This kanji visually represents a surface that is sunken or hollowed inward, like a dent or depression. It depicts the shape of something curved or pressed inward, the opposite of convex. The character's form itself mirrors the idea, with the middle portion appearing to dip below the surrounding edges.
On'yomi
おう
Kun'yomi
くぼ.む、へこ.む、ぼこ