English Reference

Word

diagonal

Phoneticsdi·ag·o·nal

US/daɪˈæɡənəɫ/

UK/daɪˈæɡənəl/

Definitions

01slanted or at an angle

B2

adj. describing a straight line that is slanted, rather than going straight across or straight up and down.

adj. having a slanted or oblique direction; neither horizontal nor vertical.

“The shirt has a pattern of diagonal stripes in blue and white.”

“The architect incorporated several diagonal support beams to give the glass atrium a more dynamic and modern aesthetic.”

02joining opposite corners

B2 · Math

adj. connecting two opposite corners of a square, rectangle, or other flat shape.

adj. joining two non-adjacent vertices of a polygon, such as the opposite corners of a quadrilateral.

“Draw a diagonal line from the top-left corner to the bottom-right corner.”

“To calculate the length of the diagonal, you must apply the Pythagorean theorem to the sides of the rectangle.”

Synonyms

crosswise

03a slanted line

B2

n. a straight line that joins opposite corners or goes across at an angle.

n. a straight line joining non-adjacent vertices of a polygon or any slanted line or direction.

“The hikers took a shortcut across the field, walking on a diagonal toward the gate.”

“The composition of the painting is dominated by a strong diagonal that leads the viewer's eye from the foreground into the distance.”

Synonyms

Real-World Examples

“Goal two: when marking Messi, Spence and Nico O’Reilly were in parallel with each other rather than being diagonal.”
The Guardian · 23 Sept 2026

Etymology

From Middle French diagonal, from Latin diagōnālis, from Ancient Greek διαγώνιος (diagṓnios, “from angle to angle”), from διά (diá, “across”) + γωνία (gōnía, “angle”).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Word family

diagonalAdjectivediagonallyAdverb

This entry

Level
B2 · Upper Intermediate
Frequency
Frequent
Updated

Scan code

englishreference.com/q/diagonal

English Reference