To determine the number of entries in a matrix, count the number of elements inside the brackets. For example, a matrix having the elements -5, 2, 10, 4, 19 and -4 has six entries.
The entries in a matrix are organized into rows and columns. The number of rows and columns are known as the dimensions. By convention, the notation for matrix dimensions is rows by columns. For example, if each row of a matrix each has two entries and each column has three entries, the matrix's dimensions are two by three. If each row has four entries and each column has three entries, the matrix's dimensions are four by three.
The position of an entry in a matrix is indicated by a subscript of the respective entry's row followed by its column. For example, if an entry a has the subscript 23, it's in the second row and the third column of the matrix. Additionally, if entry b has subscript 34, it's in the third row and the fourth column of the matrix.
The first non-zero entry in each row of a matrix is referred to as the leading entry. For example, if a row in a matrix has entries 0, -5, 1 and 3 in that order, then -5 is the leading entry.