adjective / noun

diagonal

dy-AG-uh-nul/daɪˈæɡənl/

Slanting across rather than running horizontally or vertically.

A diagonal brace runs between opposite corners of the wooden frame.

A front-facing square wooden frame with a single contrasting brace running from its bottom-left corner to its top-right corner, making the corner-to-corner slant immediately visible.

Etymology

diaGreekacross, through

+gonGreekangle, corner

+alLatinrelating to

Across and corner give the original image of a line running from one corner to a nonadjacent corner. That corner-to-corner direction explains the familiar slant across a square or rectangle.

In context

The Scroll of Shadows35:10

Take the bend, a diagonal stripe sweeping from corner to corner like a knight's sash.

25 Stunning Heraldry Designs and the Meaning Behind Knightly Symbols | Medieval History Guide

More examples

She cuts the sandwich on a diagonal.
The scarf has wide diagonal stripes.
The two diagonals of a rectangle cross at its center.

Forms

diagonal · diagonals

diagonally adverb — In a slanting direction rather than horizontally or vertically.

Similar words

slanted: Describes a tilt without suggesting a corner-to-corner direction.
oblique: Emphasizes an angle that is neither parallel nor perpendicular.