<Dd> A = (− 1.3 0.6 20.4 5.5 9.7 − 6.2). (\ displaystyle \ mathbf (A) = (\ begin (bmatrix) - 1.3&0. 6 \ \ 20.4&5. 5 \ \ 9.7& - 6.2 \ end (bmatrix)).) </Dd> <P> The numbers, symbols or expressions in the matrix are called its entries or its elements . The horizontal and vertical lines of entries in a matrix are called rows and columns, respectively . </P> <P> The size of a matrix is defined by the number of rows and columns that it contains . A matrix with m rows and n columns is called an m × n matrix or m - by - n matrix, while m and n are called its dimensions . For example, the matrix A above is a 3 × 2 matrix . </P> <P> Matrices which have a single row are called row vectors, and those which have a single column are called column vectors . A matrix which has the same number of rows and columns is called a square matrix . A matrix with an infinite number of rows or columns (or both) is called an infinite matrix . In some contexts, such as computer algebra programs, it is useful to consider a matrix with no rows or no columns, called an empty matrix . </P>

How to write the dimensions of a matrix
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