Although pH and acidity are related, they are not the same. Instead, pH is a way to measure acidity.

Acidity

Acidity refers specifically to the concentration of hydrogen (H+) ions in relation to hydroxyl (OH-) ions. A solution is defined as acidic when it has more H+ ions as compared to OH- ions. The higher the concentration of H+ ions, the more acidic the solution.

pH

pH is a numerical scale that measures how acidic or basic a solution is on a scale from 0 to 14. It's based on the concentration of H+ ions in the solution.

• A pH of neutral is neutral, indicating the solution has equal concentrations of H+
• and OH- ions.
• A pH less than 7 indicates an acidic solution – it has more H+ ions. Acidity levels
• decrease going from 0 to 7, with 0 indicating strongest acidity.
• A pH greater than 7 indicates a basic solution - it has more OH- ions. 
• Basicity levels decrease going from 14 to 7, with 14 indicating strongest basicity. 

So, pH provides a specific measurement for acidity on a defined scale but it is not the same as acidity.