A neutral substance is a substance that shows no properties of being either an acid or a base. Neutral substances also have an equal number of hydrogen ions and hydroxyl ions.
In chemistry, pH is the measure of the acidity in an aqueous solution. Any aqueous solution with a pH level of more than 7 is said to be alkaline, while solutions with a pH level lower than 7 are acidic. Neutral substances are aqueous solutions with a pH level of exactly 7. The most common example of a neutral substance is distilled water. pH is also important in practical applications such as setting up an aquarium.