In the context of organic chemistry reactions, which of the following processes involves the transfer of an acyl group to a nucleophile?

Define the term 'nucleophile': A nucleophile is a chemical species that donates an electron pair to form a chemical bond in reaction. Nucleophiles are typically rich in electrons and seek positively charged or electron-deficient sites.

Analyze each process: - Esterification involves the reaction of an alcohol with a carboxylic acid to form an ester and water, not directly involving a nucleophile receiving an acyl group. - Acylation involves the transfer of an acyl group to a nucleophile, typically in reactions such as Friedel-Crafts acylation. - Hydrogenation involves the addition of hydrogen, not related to acyl group transfer. - Hydrolysis involves breaking bonds with the addition of water, not specifically transferring an acyl group to a nucleophile.