We know that the notation `[1, 2, 3]` is used to create an array. In fact, this notation denotes a special type of array, called a (column) **vector** in Julia, as shown in the following screenshot:

To create this as a row vector (`1 2 3`), use the notation `[1 2 3]` with spaces instead of commas. This array is of type `1 x 3 Array{Int64,2}`, so it has two dimensions. (The spaces used in `[1, 2, 3]` are for readability only, we could have written this as `[1,2,3]`).

A matrix is a two- or multidimensional array (in fact, a matrix is an alias for the two-dimensional case). We can write this as follows:

Array{Int64, 1} == Vector{Int64} #> true Array{Int64, ...