Acetylation
Acetylation describes a reaction, usually with acetic acid, that introduces an acetyl radical into an organic compound.
Moreover, it is that process of introducing an acetyl group into a compound, specifically, the substitution of an acetyl radical for an active hydrogen atom. A reaction involving the replacement of the hydrogen atom of an hydroxyl group with an acetyl radical (CH3 CO) to yield a specific ester, the acetate. Acetic anhydride is commonly used as an acetylating agent reacting with free hydroxyl groups.
In biology, acetylation is used as a post-translational modification of proteins. For example, histones are acetylated as part of gene regulation.