noun
Refers to a diagonal line or direction, often used in geometry or describing positions.
正方形の対角線を引く。
Draw a diagonal line of the square.
noun
opposite angle
Specifically the angle opposite a given side or vertex in a polygon, a technical geometry term.
三角形の一辺とその対角の関係を調べる。
Examine the relationship between a side of a triangle and its opposite angle.