Minkowski-space/Several vectors/Definition

Let ${\displaystyle {}V}$ be a Minkowski space, endowed with the Minkowski form ${\displaystyle {}\left\langle -,-\right\rangle }$. A vector ${\displaystyle {}v\in V}$ fulfilling

${\displaystyle {}\left\langle v,v\right\rangle =0\,}$

is called lightlike, a vector ${\displaystyle {}v\in V}$ fulfilling

${\displaystyle {}\left\langle v,v\right\rangle <0\,}$

is called timelike, and a vector ${\displaystyle {}v\in V}$ fulfilling

${\displaystyle {}\left\langle v,v\right\rangle >0\,}$

is called spacelike.