ester

noun

es·​ter ˈe-stər 

: any of a class of often fragrant organic compounds that can be represented by the formula RCOOR′ and that are usually formed by the reaction between an acid and an alcohol with elimination of water

Examples of ester in a Sentence

Recent Examples on the Web

Hydrolyzed baobab helps strengthen, while jojoba esters condition for silky slip that keeps frizzy hair at bay. —Christa Joanna Lee, Allure, 10 Sep. 2025

The system, called self-assembling boronate ester release or SABER, acts like a three-dimensional net. —Neetika Walter, Interesting Engineering, 10 Sep. 2025

Hampden is obsessed with esters—the aromatic compounds that smell like fruit and flowers and spice. —Gina Pace, Forbes.com, 8 Sep. 2025

The new isolated diterpene esters were named caffaldehydes A, B, and C. —Hannah Millington, MSNBC Newsweek, 19 Aug. 2025

Word History

Etymology

German, from Essigäther ethyl acetate, from Essig vinegar + Äther ether

First Known Use

circa 1852, in the meaning defined above

Rhymes for ester

• esther
• fester
• jester
• nester
• nestor
• pester
• prester
• quaestor
• tester
• wester
• yester
• ancestor

Kids Definition

ester

noun

es·​ter ˈes-tər 

: an organic compound formed by the reaction between an acid and an alcohol

Medical Definition

ester

noun

es·​ter ˈes-tər 

: any of a class of often fragrant compounds that can be represented by the formula RCOOR′ and that are usually formed by the reaction between an acid and an alcohol usually with elimination of water