What is the name of a line on a drawing composed of long and short dashes?

The name of a line on a drawing composed of long and short dashes is a centerline. Centerlines are used in technical drawings and engineering designs to indicate the center of an object. They are particularly useful for symmetrical objects or components, helping to establish a reference point for measurements and alignments.

In contrast, hidden lines are depicted with a series of short dashes and are used to represent features that are not visible from the current view. Dimension lines provide measurements and are solid lines that typically have arrowheads at each end, while outlines are solid lines that represent the visible edges of an object. The distinct and specific use of long and short dashes in centerlines is what makes them an essential element in engineering and architectural drawings.