diagonal

American  

[dahy-ag-uh-nl, -ag-nl] / daɪˈæg ə nl, -ˈæg nl /

adjective

1. Mathematics.

   1. connecting two nonadjacent angles or vertices of a polygon or polyhedron, as a straight line.

   2. extending from one edge of a solid figure to an opposite edge, as a plane.

2. having an oblique direction.

3. having oblique lines, ridges, markings, etc.

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noun

1. a diagonal line or plane.

2. virgule.

3. a diagonal row, part, pattern, etc.

4. Manège. (of a horse at a trot) the foreleg and the hind leg, diagonally opposite, which move forward simultaneously.

5. diagonal cloth.

6. Mathematics. a set of entries in a square matrix running either from upper left to lower right main diagonal, or principal diagonal or lower left to upper right secondary diagonal.

7. Chess. one of the oblique lines of squares on a chessboard.

   He advanced his bishop along the open diagonal.

diagonal British  

/ daɪˈæɡənəl /

adjective

1. maths connecting any two vertices that in a polygon are not adjacent and in a polyhedron are not in the same face

2. slanting; oblique

3. marked with slanting lines or patterns

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noun

1. maths a diagonal line or plane

2. chess any oblique row of squares of the same colour

3. cloth marked or woven with slanting lines or patterns

4. something put, set, or drawn obliquely

5. another name for solidus

6. one front leg and the hind leg on the opposite side of a horse, which are on the ground together when the horse is trotting

diagonal Scientific  

/ dī-ăg′ə-nəl /

1. Connecting two nonadjacent corners in a polygon or two nonadjacent corners in a polyhedron that do not lie in the same face.

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1. A diagonal line segment.

Other Word Forms

Derived Forms

• nondiagonal
  adjective
• nondiagonally
  adverb
• diagonally
  adverb

Etymology

Origin of diagonal

First recorded in 1535–45; from Latin diagōnālis, from Greek diagṓn(ios) “from angle to angle” + Latin -ālis adjective suffix; see dia-, -gon, -al ¹

Explanation

A diagonal is made out of a straight line that's set at an angle instead of straight up or across. If you picture a square and draw a line connecting the opposite corners, that’s a diagonal line. You’ll find diagonal lines in geometry, and also in the world around you. A quarterback might throw a diagonal pass that angles across the field, or you might buy a snazzy new leotard with diagonal stripes. Diagonal can be either a noun or an adjective. You could call the steep slope of a hill a diagonal across the sky, or you could talk about the diagonal hillside reaching up toward the clouds.

Example Sentences

A different method of using diagonal play to attack was witnessed in Ecuador's loss to Ivory Coast.

From BBC • Jun. 15, 2026

SpotGamma explains that a put diagonal spread combines the sale of a shorter-dated put with the purchase of a longer-dated put at a different strike price.

From MarketWatch • Jun. 1, 2026

The chip is giant, taking up an entire 300 millimeter silicon wafer, almost a foot long across the chip’s diagonal line.

From Barron's • May 11, 2026

Downtown Los Angeles’ street grid is diagonal, a legacy of Spanish rule.

From Los Angeles Times • May 8, 2026

Not only that, but the endless diagonal rocking of the boat was having an undeniable effect on my stomach—and judging from the greenish color of the faces around me, I wasn’t alone.

From "Hollow City" by Ransom Riggs

Related Words

• crosswise
• oblique
• slanted