baseline

noun

base·​line ˈbās-ˌlīn 

often attributive

1

: a line serving as a basis

especially : one of known measure or position used (as in surveying or navigation) to calculate or locate something

2

a

: either of the lines on a baseball field that lead from home plate to first base and third base and are extended into the outfield as foul lines

b

: basepath

3

: a boundary line at either end of a court (as in tennis or basketball)

4

: a usually initial set of critical observations or data used for comparison or a control

5

: a starting point

the baseline of this discussion

Synonyms of baseline

• beginning
• start
• onset
• inception
• alpha
• commencement
• launch
• threshold

Examples of baseline in a Sentence

The experiment is meant only to provide a baseline for other studies.

any year or event we use as the baseline for the Renaissance is going to be at least somewhat arbitrary

Recent Examples on the Web

These include completing the Critical Design Review (CDR) by the end of 2026, which will establish the certifiable design baseline for the aircraft and enable the production and testing of certification-conforming models. — Bojan Stojkovski, Interesting Engineering, 18 July 2026

Worse, once that extra effort becomes routine, people forget how much simpler the work used to be, so by the time anyone asks whether the commitment has weakened, the baseline to compare against is gone. — Kerry Huang, Forbes.com, 17 July 2026

Collins’s untroubled support for Clayton reveals how far below this simple baseline her entire party has sunk. — Jonathan Chait, The Atlantic, 17 July 2026

Shifting baseline syndrome puts a name on something that most of us have experienced—the ways in which the fog of forgetting veils experience. — Literary Hub, 15 July 2026

Word History

First Known Use

circa 1556, in the meaning defined at sense 1

Rhymes for baseline

• alkaline
• andesine
• anodyne
• anticline
• arginine
• asinine
• benzidine
• borderline
• byzantine
• calamine
• caroline
• centerline

Kids Definition

baseline

noun

base·​line ˈbās-ˌlīn 

1

: a line used as a base

2

a

: either of two straight lines on a baseball field leading from home plate to first base and third base and extending into the outfield

b

: base path

Medical Definition

baseline

noun

base·​line ˈbā-ˌslīn 

: a set of critical observations or data used for comparison or a control