凹 (āo) - concave & sunken

凹Tone 1

āo ｜ 5 strokes ｜ radical: 凵

安傲

凹 · āo

concave;

sunken;

hollow;

indented;

a depression

concavesunkenhollow

Usage highlights

concave surfaceconcave lensconcave mirrorconcavesunken/convexconcave landform

Synonyms

  • 洼— depression; low-lying area
  • 陷— to sink; to cave in

Antonyms

  • 凸— convex; protruding

Usage & contexts

Examples

  • The surface is concave (凹面).
  • There is a depression in the ground (凹陷).
  • This is a concave lens (凹透镜).
  • The terrain is uneven with bumps and hollows (凹凸不平).

Collocations

  • concave surface(凹面)
  • concave lens(凹透镜)
  • concave mirror(凹面镜)
  • concave-convex(凹凸)
  • sunken/convex-concave(凹凸)
  • concave landform(凹地)

Idioms

  • Uneven with bumps and hollows(凹凸不平)
  • Convex and concave fitting together(凹凸有致)

Cultural background

FAQ
  • Represents the concept of concavity in Chinese philosophy and aesthetics, often paired with its opposite 凸 (convex).
  • Used in traditional Chinese art and calligraphy to describe brushstroke techniques and compositional balance.
  • Appears in geographical descriptions and technical terminology.

FAQ