1. A length (straight or curved) without breadth or thickness; the trace of a moving point.
2. A mark that is long relative to its width
3. A linear string of words expressing some idea
4. A formation of people or things one after another
5. A formation of people or things beside one another
6. Something long and thin and flexible.
7. A conceptual separation or demarcation:; SYN. dividing line, demarcation, contrast.
8. A fortified position (especially one marking the most forward position of troops)
9. A particular kind of product; SYN. product line, line of products, line of merchandise, business line, line of business.
10. A commercial organization serving as a common carrier.
11. Railroad track and roadbed; SYN. railway line, rail line.
12. In games or sports; a mark indicating positions or bounds of the playing area.
13. Acting in conformity; or or
14. A single frequency (or very narrow band) of radiation in a spectrum.