An **event** is something that happens instantaneously at a single point in spacetime, such as a light flashing, or a position on a moving object passing another point.

All events in spacetime are defined using the four coordinates *t*,* x* , *y*,* z*.

It is often referred as **x ^{μ}** using index notation, with μ = {0,1,2,3}

The quantity **x ^{μ}** is known as the

**four-position**(it is one example of

**four-vector**) as it describes an event or position in spacetime using the four components

*(ct,x,y,z)*.

We can think of a particule moving through spacetime as a succession of events, and if we link all these events together we would obtain a line representing the particle's travel through spacetime. This line is called the particle's **world line**.