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

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

Their Silver Rum takes inspiration from a late-17th-century Jamaican molasses recipe that is distilled in small batches in a copper pot still to produce an ester-forward Jamaican-style rum. —Hudson Lindenberger, Forbes.com, 11 Aug. 2025

Meanwhile, olive oil esters not only condition lashes, but also add a smidge of luster. —Conçetta Ciarlo, Vogue, 11 Aug. 2025

Organophosphate ester flame retardants (OPFRS) were used as an alternative to PBDEs, especially as a flame retardant in foams, furniture, and tech products. —Julia Forbes, Wired News, 22 July 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