diagonal
adjective
[ dʌɪˈaɡ(ə)n(ə)l ]
• (of a straight line) joining two opposite corners of a square, rectangle, or other straight-sided shape.
diagonal
noun
• a straight line joining two opposite corners of a square, rectangle, or other straight-sided shape.
Origin:
mid 16th century: from Latin diagonalis, from Greek diagōnios ‘from angle to angle’, from dia ‘through’ + gōnia ‘angle’.
