The IUPAC name of the acid present in vinegar is:

Vinegar is a solution of 4-6% of acetic acid( CH₃COOH) in water.

According to IUPAC nomenclature rule, CH₃COOH contains two carbon atoms. So, the root word 'eth' should be used for two carbon atoms. As the functional group of carboxylic acid is COOH , so the suffix "oic acid" should be used.

So the IUPAC name of CH₃COOH is Ethanoic acid.

Acetic acid is the common name of ethanoic acid.