Meaning of acid:
A chemical that gives off hydrogen ions in water and forms salts by combining with certain metals. An example of an acid is hydrochloric acid. Acids have a sour taste and turn certain dyes red. Some acids made by the body, such as gastric acid, can help organs work the way they should. Acidity is measured on a scale called the pH scale. On this scale, a value of 7 is neutral, and a pH value of less than 7 to 0 shows increasing acidity.