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

Keto supplements, including capsules, powders, and liquids, are more likely to contain ketone esters or salts. —Melissa Nieves, Verywell Health, 18 Mar. 2025

Malting enhances esters in the rye, producing lighter fruity notes of apple, pear, and even citrus zest. —Joseph V Micallef, Forbes, 12 Dec. 2024

Each of these must be converted to retinoic acid, with retinyl esters being the weakest and retinal being the strongest. —Jessica Swirble, Verywell Health, 19 Feb. 2025

Key Ingredients: Squalane, cholesterol esters, vitamin E, vitamin C, retinyl palmitate, Morinda citrifolia extract, and Padina pavonica. —Kiana Murden, Vogue, 21 Feb. 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