Definition of diagonal in English:


Line breaks: di¦ag|onal
Pronunciation: /dʌɪˈag(ə)n(ə)l



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  • 1A straight line joining two opposite corners of a square, rectangle, or other straight-sided shape.
    More example sentences
    • Do this at a diagonal, from one corner of the square to the opposite corner.
    • For example, the Pythagoreans did not expect to uncover irrational numbers in the diagonal of a square.
    • The particular tablet which concerns us is not one relating to administration but one which presents a geometrical problem which asks for the dimensions of a rectangle whose area and diagonal are known.
  • 1.1 Mathematics The set of elements of a matrix that lie on a line joining two opposite corners.
    More example sentences
    • The alpha values and the mean interitem correlations are presented in the diagonals of the matrices in Table 2.
    • The diagonal of the rate matrix is specified such that the row sums are equal to zero.
    • If we restrict ourselves to the 2x2 arrays whose diagonals lie on the main diagonal of the table, then the sum of four numbers in the array is always a perfect square.
  • 1.2A slanting straight line: the bars of light made diagonals across the entrance tiles can be laid on the diagonal
    More example sentences
    • Let stand ten minutes, then slice very thin and on the diagonal.
    • Take cuttings from last seasons growth, cut just below the bud and trim the top on the diagonal.
    • The paintings are thick with diagonals; light is pure color, color is pure stroke.
  • 1.3 Chess A slanting row of squares whose colour is the same.
    More example sentences
    • If you move a pawn to open up a diagonal for a bishop, then should you usually NOT move up another pawn to develop the bishop on the other diagonal.
    • After a queen pawn opening, Hort threatened mate on the long diagonal.
    • As frequently happens in such a situation, White does not have a diagonal for his dark Bishop, nor does he have any other diagonals from which to aim at his opponent's King.


mid 16th century: from Latin diagonalis, from Greek diagōnios 'from angle to angle', from dia 'through' + gōnia 'angle'.

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