Concept:Vinegar is a dilute solution of acetic acid in water.Explanation:Acetic acid (CH3​COOH) is the second member of the carboxylic acid series after formic acid.Its IUPAC name is ethanoic acid.A dilute solution containing about 5–20% acetic acid in water, along with other trace chemicals, is known as vinegar.Thus, acetic acid is the main constituent responsible for the sour taste and preservative properties of vinegar.Vinegar is commonly used as a preservative and as a cooking acid.Answer:Acetic acid.