Other forms: diagonals
Diagonal means running slantwise from corner to corner. A diagonal line, cut diagonally, the diagonal stripe.
In a rectangle the diagonal is the longest straight line inside it, and in a square it is the side times the square root of two — the first irrational number anybody found. In chess, bishops move along diagonals. In sewing, cutting on the diagonal is cutting on the bias, which makes cloth stretch. Note diagonally; and that a diagonal crossing at a junction is called a scramble crossing.
1adjectivediagonalRunning slantwise from corner to corner.
“The flag has a bold diagonal stripe of red across a blue background.”
2nounlineSuch a line.
“Draw a diagonal across the square to divide it into two triangles.”
diagonal is a slanting line.
Greek diagonios means from angle to angle — dia, across, plus gonia, an angle. Polygon, pentagon and trigonometry come from the same angle.
Ancient Greek
διαγώνιος — from angle to angle
Latin
diagōnālis
Middle French
diagonal
English, today
diagonal
Built from
From Middle French diagonal, from Latin diagōnālis, from Ancient Greek διαγώνιος (“from angle to angle”), from διά (“across”) + γωνία (“angle”).
Etymology from Wiktionary, CC BY-SA
Practised in Directions & Position, Chess & Card Games