#matrix  a rectangular array of elements (or entries) set out by rows and columns
  supertype:  #array  an orderly arrangement: "an array of troops in battle order"
  subtype:  #correlation_matrix__correlationmatrix  a matrix giving the correlations between all pairs of data sets
  subtype:  #dot_matrix__dotmatrix  a rectangular matrix of dots from which written characters can be formed
  subtype:  #square_matrix  a matrix with the same number of rows and columns
     subtype:  #diagonal_matrix__diagonalmatrix  a square matrix with all off-diagonal elements equal to zero
        subtype:  #scalar_matrix  a diagonal matrix in which all of the diagonal elements are equal
           subtype:  #identity_matrix__unit_matrix  a scalar matrix in which all of the diagonal elements are unity
     subtype:  #determinant  a square matrix used to solve simultaneous equations
     subtype:  #Latin_square  a square matrix of n rows and columns; cells contain n different symbols so arranged that no symbol occurs more than once in any row or column
     subtype:  #magic_square__magicsquare  a square matrix of n rows and columns; the first n-squared integers are arranged in the cells of the matrix is such a way that the sum of any row or column or diagonal is the same
     subtype:  #nonsingular_matrix__nonsingularmatrix  a square matrix whose determinant is not zero
     subtype:  #singular_matrix  a square matrix whose determinant is zero
  subtype:  #real_matrix  a matrix whose elements are all real numbers

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