Acyl halides, also known as acid chlorides, are important compounds used in many chemical industries for the synthesis of organic compounds. They are highly reactive and are found in many chemical reactions. There are several synonyms for the word 'acyl halide' that are commonly used in literature. One widely used synonym is 'acid chloride', which refers to the replacement of the hydroxyl group of a carboxylic acid by a halogen during the formation of the acyl halide. Another synonym for this compound is 'acyl chloride', which is derived from the acyl group (-CO) and a halogen atom. Additionally, the term 'haloformate' is used to refer to certain types of acyl halides in which the acyl group is bonded to a carbonyl group and a halogen atom.