diagonal
UK[daɪˈæɡənəl]US[daɪˈæɡənəl]
adj
(of a straight line) joining two opposite corners of a square, rectangle, or other flat shape at an angle
n
a straight line joining two opposite corners of a square, rectangle, or other flat shape
Morpheme Breakdown
dia
gon
al
dia
across
gon
angle
al
adjective suffix
Etymology
The word 'diagonal' has a clear geometric logic rooted in ancient Greek. It is formed from the combination of 'dia-', meaning "across" or "through", and 'gonia', meaning "angle" or "corner". Literally, it describes a line that goes "from angle to angle". This term entered Late Latin as 'diagonalis' before being adopted into Middle English. The modern meaning retains this precise literal sense, referring specifically to a straight line connecting non-adjacent vertices of a polygon, perfectly encapsulating its original components.
Analysis
Structure: dia (across) + gon (angle) + al (adjective suffix)
dia: Greek origin, meaning "through, across, apart".
gon: Greek origin (from 'gonia'), meaning "angle, corner".
al: Latin adjectival suffix, meaning "pertaining to, of the kind of".
Examples
Draw a diagonal line from the top left corner to the bottom right.
The tablecloth had a pattern of diagonal stripes.
The bishop in chess moves any number of squares along a diagonal.