How to Write 凸 (tū) — Meaning “Convex; protruding”

Imagine a small hill with a flat top: the top horizontal line is the peak, the sides slope down, and the bottom is a valley (the 凵 radical). This hill shape looks like a bump sticking out, reminding you of the meaning "protruding."

Write the top horizontal stroke first, then the left vertical, then the short middle horizontal, then the right vertical, and finally the bottom horizontal. A common mistake is making the middle section too wide; keep it narrow so the character looks balanced like a small bump.

凸 (tū) means convex like a bump, while 凹 (āo) means concave like a dent — visually opposite shapes. 凶 (xiōng) means fierce and has an X-like shape inside a box; it has nothing to do with shape or protrusion, so the meanings are completely different.

凸 appears in technical terms like 凸透镜 (convex lens) and describes things sticking out, such as a bump on a road or a bulge in a surface. It is not common in daily conversation but is used in textbooks, geometry, and descriptive writing with no special cultural associations.

Common words containing 凸 include: 凸出 (tū chū) — To protrude; to stick out; 凸透镜 (tū tòu jìng) — Convex lens; 凸起 (tū qǐ) — To bulge; to protrude.