Definition - What does pH mean?
pH is a figure that represents potential hydrogen, and is the measure of acidity or alkalinity in any water-soluble substance. pH values are represented on a logarithmic scale with numbers 1-14 with 7 being a neutral point. Values below 7 indicate acidity with lower numbers indicating greater acidity. Numbers higher than 7 indicate alkalinity with higher numbers indicating greater alkalinity.
Safeopedia explains pH
pH is the balance between hydrogen ions and hydroxide ions. Ions are atoms that have lost or gained an electron and hold a positive or negative charge. Everything has a pH value that can be measured. Determining the pH of a particular substance has a number of important applications, such as determining soil quality by it's acidity or alkalinity.