Definition:
pH: refers to the hydrogen ion concentration in an aqueous solution. Olive oil and other oils are not water soluble so their acidity cannot be measured in terms of pH. Vegetable oils are very weak acids, when mixed with a strong base such as lye they will form a salt (commonly called soap). Better oils have a low acidity while lower quality oils will be more acidic. Their acid content is usually measured in percent free acidity. Extra virgin olive oil must have less than .8% free fatty acid but some have less than .1%