Diagonal

How to spell diagonal

8 letters · 4 syllables

How to pronounce diagonal

Say the part in capitals loudest.

What does diagonal mean?

1. adjectiveRunning at a slant, joining two opposite corners rather than going straight across or up and down.
2. nounA straight line that joins two opposite corners of a shape.

Diagonal in a sentence

• adjective

  The tailor cut the fabric on a diagonal line to make it stretch.

• noun

  The carpenter measured the diagonal to check that the frame was square.

• adjective

  A diagonal crack ran from one corner of the ceiling to the other.

• noun

  She folded the napkin along its diagonal to make a neat triangle.

Where does diagonal come from?

Language of origin: Greek

The word comes from the Greek diagonios, which described a line running 'from angle to angle', built from dia 'across' or 'through' and gonia 'angle' or 'corner'. The Romans adopted it as the Latin diagonalis, used by geometers for the straight line joining two non-adjacent corners of a figure. English took it up in the late 1500s, first as a strict geometrical term and only later as the looser everyday adjective for anything set at a slant. The gonia root is the same one that surfaces in 'polygon' (many angles) and 'pentagon' (five angles), so picturing an angle helps fix the single g and the -gon in the middle. The unstressed schwa in the final 'nal' is the main spelling trap, since the ending sounds like 'nul' but is written -nal.

How the word is built

• dia- (across, through)
• gon (angle, from Greek gonia)
• -al (adjective/noun suffix)