# Definition:Time/Fourth Dimension

## Definition

In the Theory of Relativity, it is convenient to consider time as another dimension in addition to, and treated similarly to, the $3$ dimensions of ordinary space.

## Historical Note

The treatment of time as the $4$th dimension originates with Albert Einstein.

While introduced as a mathematical convenience, the concept took hold in popular culture as a pseudo-scientific backing for an entire subgenre of science fiction: the time-travel story.