Column Matrix

Sometimes (as in the question) we are interested only in direction, not location, nor length. Use a vector for this. Its length does not matter. Often it will be given a length of one.

A geometric vector may be represented with a list of numbers called a column matrix. A column matrix is an ordered list of numbers written in a column. Here is an example of a column matrix:

Each number of the column matrix is called an element. The numbers are real numbers. The number of elements in a vector is called its dimension. A row matrix is an ordered list of numbers written in a row. Here is an example of a row matrix:

(12.5, -9.34)

To be consistent, our vectors will always be represented with column matrices. Some books represent vectors with row matrices, which makes no fundamental difference, but affects how formulas look.