A line is a series of points strung together to form a chain. FME allows degenerate lines of all kinds to be stored, but they may not function well during processing or writing. For example, duplicate consecutive points or self-intersections may require cleanup by FME Transformers at some point in the workflow.
A line may have coincident first and last points (be closed), and may still be considered a Line. If desired, it can be converted to an area using transformers.
fme_geometry = fme_line
fme_type = fme_line