If the concentration of hydrogen ions (H+) is greater than the concentration of hydroxide ions (OH-) in a solution, the solution is acidic.

Here's why:

* pH scale: The pH scale measures the acidity or alkalinity of a solution.

* Hydrogen ions and acidity: A higher concentration of hydrogen ions indicates a stronger acid, and therefore a lower pH value.

* Hydroxide ions and alkalinity: A higher concentration of hydroxide ions indicates a stronger base, and therefore a higher pH value.

Therefore, if [H+] > [OH-], the pH will be less than 7, indicating an acidic solution.