Final answer:
The functional group found in an ester is the ester functional group, which consists of an acyl group bonded with an alkoxy group.
Step-by-step explanation:
An ester is an organic compound that is a derivative of a carboxylic acid. The functional group found in an ester is the ester functional group, which consists of an acyl group bonded with an alkoxy group. The general structure of an ester is R-C-OR', where R represents the carboxylic acid portion and R' represents the alcohol portion.
For example, in the ester ethyl acetate (CH3COOC2H5), the acyl group is CH3CO- and the alkoxy group is C2H5-. The ester functional group is responsible for the characteristic properties and chemical reactions of esters.