Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of an acetylcholine stimulus. [ http://purl.obolibrary.org/obo/go/references/0000071 GOC:TermGenie http://www.ncbi.nlm.nih.gov/pubmed/21238497 ]