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

Founders who recently had one exceptional year sometimes assume that year represents their new baseline, when a buyer will more likely average the last three years, or discount the outlier entirely. — Lien De Pau, Forbes.com, 29 Aug. 2026

The court had also been used for basketball, with the hoops still up behind the baseline. — Albert Samaha, New Yorker, 29 Aug. 2026

The goal is to establish a user’s baseline and flag meaningful changes over time. — Hanna Wickes, Fort Worth Star-Telegram, 27 Aug. 2026

The number uses an unrealistic 2001 baseline that projected endless surpluses, as if the late-1990s revenue windfall would last forever. — Veronique De Rugy, Oc Register, 27 Aug. 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