baseline

Pluralbaselines

Formsbaselines, baselining, baselined

1. 1
   nouncountable

   A known value, set of data, condition, or established configuration used as a fixed reference point for measurement or comparison.

   Researchers measured each patient's resting heart rate to establish a baseline.

   Using 1990 emissions as the baseline, the city has cut its carbon output by a third.

   UsageUsually establish or set a baseline, then measure against it: compared against the baseline.

   Similarbenchmark, reference, standard, yardstick

2. 2
   end mark (tennis)nouncountable

   The line at each far end of a tennis court that marks the boundary of the area of play.

   She hit a deep forehand that clipped the baseline for a winner.

   The ball landed an inch beyond the baseline, and the line judge called it out.

   Note

   The line belongs to the court, so during a rally a ball that clips the baseline inside the sidelines in play is in, and an umpire who calls it out has missed the call. The lines that run down the long sides of the court are the sidelines. Source

   Checked 31 Oct 2026 · 3 facts

   • The baseline itself is part of the court. usta.com
   • This applies to a rally ball landing on the baseline within the relevant sidelines. A serve landing on the baseline is a fault; in singles, the baseline beyond the singles sidelines is outside the singles court. itftennis.com
   • The lines along the long sides of a tennis court are called sidelines. itftennis.com
3. 3
   surveyingnouncountable

   A line that serves as the base from which measurements are taken or construction is laid out.

   Surveyors marked a baseline along the road and measured every lot from it.

   The carpenter snapped a chalk baseline across the deck to keep the boards straight.

4. 4
   record at startverbtransitive

   To establish a baseline for something, giving later measurements a fixed reference to be compared with.

   Teams should baseline performance at the start of every project.

   The schedule was baselined in January, and every delay since has been measured against it.

   UsageOften passive: a schedule is baselined, then changes are measured against it.

   Note

   The verb is at home in the passive: a test, a schedule or a grammar is baselined, and from then on changes are tracked against it. Lojban's Questions and Answers glosses the word in parentheses, saying the language's grammar and core vocabulary have been baselined (frozen) for several years.

5. 5
   verbintransitive

   To play from the baseline, staying back at the far end of the court during rallies.

   Note

   The -ing form names a whole style of play: baselining means staying back and trading shots from the far end rather than coming forward. Susan Orlean, in The Bullfighter Checks Her Makeup, writes of a younger player for whom baselining was no longer enough to win points, so she learned to move around the court. Source

   Checked 31 Oct 2026 · 2 facts

   • Susan Orlean wrote The Bullfighter Checks Her Makeup, which includes her tennis essay "The Three Sisters". catalog.freelibrary.org
   • Orlean describes a younger player who learned to move around the court because baselining was no longer enough to win points. newyorker.com

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