![reference frame reference frame](https://www.tekportal.net/wp-content/uploads/2018/12/reference-frame.png)
noun Physics.
- A basis of a four-dimensional coordinate system in which the first coordinate is understood as a time coordinate, while the other three coordinates represent spatial dimensions. Inertial frames and non-inertial frames are both examples of reference frames. Also called frame of reference See also General Relativity space-time Special Relativity.