1. Extending from one angle to an opposite of a quadrilateral or multilateral figure, and dividing it into two.

2. Right line so drawn.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• diagonel,
• diaginol,
• diagonial,
• diagnal,
• diagnol,
• diaginaly,
• diaganal,
• diagnoal,
• diagonse,
• diagagonal,
• diagonol,
• diginal,
• reagonal,
• diagonis,
• diagional,
• diagnel,
• diagonly,
• dignal,
• diaganol,
• diaginal

• diagonalise,
• diagonally,
• diagonalize.

The adjective form of the word "diagonal" is "diagonal".

The plural of the "diagonal" can be the "diagonals".

The singular of the "diagonal" can be the "diagonal".