right-angle
UK[ˈraɪt ˌæŋɡl̩]US[ˈraɪt ˌæŋɡl̩]
n
an angle of 90°, as in a corner of a square
Morpheme Breakdown
right
angle
right
correct, straight
angle
space between intersecting lines
Etymology
The term 'right-angle' is a transparent English compound formed from two ancient roots. The word 'right' carries its original Proto-Indo-European sense of "straightness" or "directness," which evolved into the geometric concept of perpendicularity. 'Angle' descends from a root meaning "to bend" or "corner." The compound's logic is brilliantly literal: it describes the angle that is "straight" or "correct" in the sense of being perfectly upright, forming a quarter of a full rotation. This term exemplifies how everyday geometric language preserves precise, ancient spatial concepts.
Analysis
Structure: right (correct, straight) + angle (space between intersecting lines)
- right: From Old English riht (straight, direct, correct), from Proto-Germanic rehtaz, from Proto-Indo-European h₃reǵtós (having moved in a straight line). In this compound, it functions as an adjective modifying 'angle' to specify a type.
- angle: From Old French angle, from Latin angulus (corner), from Proto-Indo-European h₂engulos (bend). It is the core noun denoting the geometric figure.
Examples
A square has four equal sides and four right-angles.
The carpenter used a set square to ensure the joint formed a perfect right-angle.
In a right-angled triangle, the side opposite the right-angle is called the hypotenuse.