diagonal

1 of 2

adjective

di·​ag·​o·​nal dī-ˈa-gə-nᵊl 

-ˈag-nəl

1

a

: joining two vertices of a rectilinear figure that are nonadjacent or two vertices of a polyhedral figure that are not in the same face

b

: passing through two nonadjacent edges of a polyhedron

a diagonal plane

2

a

: inclined obliquely from a reference line (such as the vertical)

wood with a diagonal grain

b

: having diagonal markings or parts

a diagonal weave

diagonal

2 of 2

noun

1

: a diagonal straight line or plane

2

a(1)

: a diagonal direction

(2)

: a diagonal row, arrangement, or pattern

b

: something oriented in diagonal position

3

: slash sense 4

see also:

on the diagonal

Synonyms of diagonal

Adjective

• oblique
• sloping
• leaning
• sloped

Noun

• slope
• inclination
• incline

Examples of diagonal in a Sentence

Adjective

The blanket is covered with diagonal stripes.

the diagonal design ran up the wall all the way from the lower left to the upper right-hand corner

Noun

a design with strong diagonals

the ramp was set at a low diagonal to make it easier for physically challenged patrons

Recent Examples on the Web

Adjective

On Sunday and Monday night of this week, June 14 and 15, Venus, Jupiter and Mercury will be lined up fairly close to each other in a nearly perfect diagonal row in the low western early evening sky. —Mike Lynch, Twin Cities, 14 June 2026

Their images divide the diagonal axis almost exactly into thirds. —Literary Hub, 10 June 2026

Noun

The dog is ahead and has stopped by the tree that bisects the diagonal; the girl with the bright red coat who seems to be paused behind him. —Literary Hub, 10 June 2026

In Michael Saylor's Strategy, one trader sold 29,425 of the 125/180-call diagonals, collecting about $56 million in the process. —Tyler Bailey, CNBC, 9 June 2026

Word History

Etymology

Adjective

Latin diagonalis, from Greek diagōnios from angle to angle, from dia- + gōnia angle; akin to Greek gony knee — more at knee entry 1

First Known Use

Adjective

1563, in the meaning defined at sense 1a

Noun

1571, in the meaning defined at sense 1

Phrases Containing diagonal

• diagonal matrix
• on a diagonal
• on the diagonal
• principal diagonal

Rhymes for diagonal

• hexagonal
• octagonal
• tetragonal

Kids Definition

diagonal

1 of 2 adjective

di·​ag·​o·​nal dī-ˈag-ən-ᵊl 

-ˈag-nəl

1

: joining two opposite corners of a four-sided figure

2

: running in a slanting direction

diagonally

-ən-ᵊl-ē, 

-nə-lē

adverb

diagonal

2 of 2 noun

1

: a diagonal line or direction

2

: a diagonal row, arrangement, or pattern

3

: slash entry 2 sense 2