Baseline

[Renato]

a line on a sports field, such as the one in tennis, that marks the end of the playing area, or the one in baseball that marks the path along which players run:

[LindaArrit]

the back line bounding each end of a tennis or handball court; when serving the server must not step over this line

[Quadirdith 0]

the lines a baseball player must follow while running the bases

[Michiko]

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

[mehmood]

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

[sky]

A line used as the basis for the alignment of glyphs.

[MiguelANymn]

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

[Kit]

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

[sumon9999]

To provide a baseline for measurement.

[Gornwexy 0]

To play from the baseline.

[Welington Mina]

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

[AliceAstes]

In the United States Public Land Survey System, a baseline is the principal east-west line upon which all rectangular surveys in a defined area are based. The baseline meets its corresponding meridian at the point of origin, or initial point, for the land survey. For example, the baseline for Nebraska and Kansas is shared as the border for both states, at the 40th parallel north.
More specifically a baseline may be the line that divides a survey township between north and south.
Often, a baseline is marked by other features such as a road or boundary between counties.