baseline

noun Also base line.

1. Baseball. the area between bases within which a base runner must keep when running from one base to another.
2. Tennis. the line at each end of a tennis court, parallel to the net, that marks the in-bounds limit of play.
3. (in perspective drawing) a horizontal line in the immediate foreground formed by the intersection of the ground plane and the picture plane.
4. a basic standard or level; guideline: to establish a baseline for future studies.
5. a specific value or values that can serve as a comparison or control.
6. Typography. the imaginary line on which the bottoms of primary letters align.
7. Surveying. See under triangulation(def 1).
8. Electronics. a horizontal or vertical line formed on the face of a cathode-ray tube by the sweep of the scanning dot.
9. Naval Architecture. a line on the body plan or sheer plan of a hull, representing a horizontal reference plane for vertical dimensions.

adjective

10. basic or essential.

noun

1. surveying a measured line through a survey area from which triangulations are made
2. an imaginary line, standard of value, etc, by which things are measured or compared
3. a line at each end of a tennis court that marks the limit of play

n.

also base-line, 1750, originally in surveying, from base (n.) + line (n.). Baseball diamond sense is from 1867. Baseline estimate in use by 1983.