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

• beginning
• start
• onset
• alpha
• inception
• 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

The analysis combined the results from two major long-baseline experiments that send beams of muon neutrinos across hundreds of miles to distant detectors. —Georgina Jedikovska, Interesting Engineering, 23 Oct. 2025

The indexes measure costs against a January 2018 baseline. —Meghan Hall, Sourcing Journal, 23 Oct. 2025

His research shows a higher baseline for consistent activism in 2025 than in 2017. —Sarah D. Wire, USA Today, 23 Oct. 2025

In the trial with a placebo, those in the cannabis group had, on average, about a 30% drop in pain after 12 weeks compared to their baseline. —NPR, 20 Oct. 2025

Word History

First Known Use

circa 1556, in the meaning defined at sense 1

Rhymes for baseline

• acridine
• alkaline
• andesine
• anodyne
• anticline
• arginine
• asinine
• atropine
• benzidine
• borderline
• byzantine
• calamine

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