In the context of geometry, a translation is a type of transformation in which the movement of a figure occurs along a line, as shown in the figure below:

In the figure above, the figure is translated horizontally. Translation can also occur both vertically and diagonally. In any of these cases, the only aspect of the figure that changes is the location of the figure in the space. The dimensions and rotational position of the figure remain constant. This is what is meant by the figure being moved along a line.

See also transformation, reflection, rotation.