A unit vector is any vector that is one unit in length. Unit vectors are often notated the same way as normal vectors, but with a mark over the letter (e.g. being the unit vector of .)
To make a vector into a unit vector, one just needs to divide it by its length: . The resulting unit vector will be in the same direction as the original vector.
Three common unit vectors used in component form are , and , referring to the three-dimensional unit vectors for the x-, y- and z-axes, respectively. They are commonly just notated as i, j and k.
They can be written as follows:
For the unit vector corresponding to the -th basis vector of a vector space, the symbol (or ) may be used.