A line that is a base for measurement or for construction.

A datum used as the basis for calculation or for comparison.

(typography) A line used as the basis for the alignment of glyphs.

(tennis) The line at the farthest ends of the court indicating the boundary of the area of play.

(engineering) A configuration of software, hardware, or a process that is established and documented as a point of reference.

(engineering, computing) To provide a baseline for measurement.

(tennis) To play from the baseline.