直角 (zhí jiǎo) literally means 'straight angle' and refers to an angle measuring exactly 90 degrees. The character 直 means 'straight' or 'direct', conveying the idea of perpendicularity, while 角 means 'angle' or 'corner'. Together, they denote the geometric concept where two lines or line segments intersect to form a perfect L-shape — the foundation of rectangles, squares, and many architectural and engineering designs.

This term is commonly used in mathematics education, geometry problems, construction, carpentry, and everyday descriptions of shapes and spatial relationships. It appears frequently in textbooks, technical drawings, and instructions involving alignment or measurement. Unlike more abstract angle terms like 钝角 (obtuse angle) or 锐角 (acute angle), 直角 has a precise, unambiguous measurement and is often verified using tools like a set square or protractor.