Which feature distinguishes a topographic map from a regular map?

A topographic map is specifically designed to represent the three-dimensional surface of the Earth in a two-dimensional format, and it does this most distinctly through the use of contour lines. These lines connect points of equal elevation and provide critical information about the terrain's shape and slope. The presence of contour lines allows users to visualize changes in elevation and understand the topography of the landscape, which is essential for activities such as hiking, planning construction, or understanding drainage patterns.

Other features, such as road markings, geographic regions, and color schemes, may appear on various types of maps, including regular maps. However, they do not convey the critical elevation data that contour lines provide. Thus, contour lines are the distinguishing feature that sets topographic maps apart from standard reference or thematic maps.