Translation guide
The English word 'convex' describes a surface or shape that curves outward, like the outside of a sphere. In Japanese, the most common equivalent is 凸面 (とつめん) or the adjective 凸状の (とつじょうの). However, depending on context, other expressions like 出っ張った (でっぱった) or 膨らんだ (ふくらんだ) may be more natural.
Describing a surface or object that bulges outward
The standard technical term for a convex surface. Used in geometry, optics, and engineering.
このレンズは凸面です。
This lens is convex.
Adjectival form meaning 'convex-shaped'. Common in descriptions of objects.
凸状の鏡
a convex mirror
Colloquial term meaning 'sticking out' or 'protruding'. Used for everyday objects, not technical contexts.
その壁は少し出っ張っている。
That wall is a bit convex.
Means 'swollen' or 'bulging'. Suitable for soft or rounded convex shapes.
膨らんだ形のクッション
a cushion with a convex shape
Referring to convex sets, functions, or polygons
In casual conversation, using 凸面 or 凸状 may sound overly technical. Instead, describe the shape with words like 出っ張っている (sticking out) or 丸みを帯びた (rounded).
Convex polygon. Standard term in geometry.
凸多角形の内角はすべて180度未満です。
All interior angles of a convex polygon are less than 180 degrees.